The 11:00 slot shows 14 tickets left online. The front desk swears the gallery is already packed. A school group coordinator calls to say their reservation for that same hour isn’t showing up anywhere. All three are looking at the same Altru event, and all three are partly right.
The number on a calendar isn’t one number. It’s capacity minus a few kinds of usage, and each kind gets counted slightly differently depending on how your programs and events are set up. Once you know what feeds the math, most “the calendar is wrong” reports turn out to be a setup question you can answer in a few minutes.
The basic formula
For a scheduled program, availability for a given time slot is the event’s capacity minus what has already been committed against it. In practice, “committed” usually includes:
- Tickets sold through daily sales and advance sales, including web form purchases.
- Group sales reservations assigned to that event, which can hold seats before they’re paid for.
- Anything else your configuration counts against capacity, such as items held during an in-progress transaction. How long those holds last, and whether they apply to your setup, is worth confirming with a test rather than assuming.
Refunds and exchanges should release capacity back to the event. If they don’t seem to, check whether the original order was actually refunded in Altru or only marked as handled outside it.
Where the capacity number comes from
This is where most confusion starts. Capacity can be set at more than one level, and staff often edit the one they can see without realizing another one is in play.
The event itself
Each event (one date and time of a scheduled program) carries its own capacity. When programs are created with a recurring schedule, every event typically inherits the program’s default. If someone later changes the default, events that were already generated may keep the old number. That’s the classic reason one Saturday shows 150 and the next shows 200.
Locations and resources
If your events are tied to a location with its own capacity, the effective limit may be the smaller of the two. Two programs sharing one room can also pull from the same physical space even though each event looks separate on its own. If you’re unsure how your version handles shared locations, build a test program in a sandbox, sell into it, and watch both events.
Price types don’t each have a pool
Adult, child, senior, and member tickets generally all draw from the same event capacity. A slot with 20 remaining has 20 seats total, not 20 per price type. If you need a cap on a specific audience (say, a limited number of member-free tickets), that usually requires a separate program or event, or a manual policy.
Why the numbers disagree
When the website, the desk, and a report show different availability for the same slot, work through these in order:
- Timing. A website calendar may refresh on a schedule or cache results. A sale at the desk two minutes ago might not show online yet. Ask how often your calendar pulls from Altru.
- Group reservations. Desk staff may see seats as “open” because no one has walked in, while a group reservation has already claimed them. Check the event for reservations, not just ticket sales.
- Combination or package items. A combo ticket that includes a timed program counts against that program’s event. Staff who only look at standalone sales will undercount.
- Edited capacity on one event. Compare the event’s capacity with the program default. If they differ, someone changed it, and that may be intentional (a private rental, a closed gallery) or a mistake.
- Different questions being asked. A report of tickets scanned answers “who’s in the building.” Availability answers “who’s booked.” Those will never match on a day with no-shows.
A query worth keeping
Build a query on scheduled program events with the date, time, program name, capacity, and quantity sold or reserved. Filter to the next 30 days. Sorting by capacity quickly surfaces events whose limit doesn’t match the rest of the series. Running this weekly before school-group season catches most surprises before a coordinator does.
If you can’t find a field that reports reserved quantity directly, say so to your team rather than guessing from sales alone, and ask Blackbaud support which output fields reflect group sales holds in your version.
What guests actually see
The guest only needs one thing from all of this: a trustworthy answer to “can I get in at 11:00?” That means showing sold-out times clearly, hiding past slots, and pulling availability often enough that the last few tickets aren’t oversold. If your web calendar lags behind the desk, consider holding back a small buffer of capacity online during your busiest stretches.
Video walkthrough
This short video covers timed-ticket calendars and availability, and pairs well with the checklist above.
Showing Altru availability on your website
The capacity math lives in Altru, and that’s where to fix it. Displaying it well is a separate job. Our Calendar Builder creates embeddable timed-ticketing calendars for your website with real-time availability from Altru, so the number a guest sees online reflects the same events your staff are selling against.
Quick answers
Do member tickets count against capacity?
If they’re issued as tickets for a timed event, generally yes. They take a seat like any paid ticket.
Why did changing the program capacity not update every date?
Events that already exist can keep the capacity they were created with. Check and edit the individual events, or confirm in a sandbox how your version applies program changes.
Can I oversell on purpose for no-shows?
The simplest approach is raising the event capacity slightly above your usual sell-out point, while staying within the space’s legal occupancy limit. Make it a written policy so desk staff don’t each do it differently.
