To set this limit, click on the Gear icon in the upper right-hand side and then ADVANCED SETTINGS.
Scroll down to the section labeled "Person Categories". You are able to create up to 8 different Person Categories and have the ability to name each category to cover any of your customer population that you specify pricing for (example: Adults, Children, Seniors, Students, etc.).
Click the orange SAVE button before leaving the page to complete your changes.