Pricing Rule - Maximum Seat clarification

Is Maximum Seat in the General Tab on Pricing Rules:

-looks against the Pricing Rule itself, or

-across all products selected in the Pricing Rule under the Criteria area?

What we want is to offer is 1/2 price tickets to 20 seats per performance. Once the 20 seats are sold, no more 1/2 price seats can be sold.

We have 100+ performances that we want to offer this to. Is this one pricing rule; or 100+ individual pricing rules?

-Jessica