Oftentimes when running a fundraising event you have a limit on the number of tickets you can sell in total. In addition to being able to set maximums & minimums on tickets per order, as well as custom quantities on a per-ticket basis, you can now set an overall capacity limit on tickets sold.
Let's say you are hosting your annual Gala at a local venue with 200 available seats. You know that 50 of those will be dedicated to VIP Tables, but the rest can be any combination of General Admission or Premium.