To be able to configure the attendance fees to activities we will go to:

Customers → General Rates → Group classes Activity Fees

From here we will access the next window, where we will see a list of quotas, where we can add more with "New", edit any of the existing ones with or even remove some with .

If we click on the button to edit some of them will open the following window:

From here, in the General section of the menu on the left, we can choose which activities are included:

While in the Prices section, we can have different rates, if we want individual or collective classes and what price has each one of them.