Usually 1 pop for the advertised price, you can usually ask for another one for more $$$, or tell the agent upfront that you want 2 sessions. If you pop really quickly i.e. 10 seconds (trust me that has happened more than once to many of us), just offer her some $$$ for one more time, she'll most likely be happy to oblige.
P.S. Don't expect a second pop for free, if you go to a restaurant and you want another steak cuz the first one wasn't big enough, I'm pretty sure you'll pay for the second steak