How to Setup QuickCal / Booked as Shown in the Demo (Embark)

There are number of ways that the plugin can be setup. For the main plugin documentation see this article.

On the Embark live demo, we have it setup with online payments where customers can select between two different booking types and choose the group amount to pay for. You can view this Tour as an example:

You can select one or multiple tickets for Adult, Child - or it could be whichever options you setup.

That was done by using WooCommerce (which integrates with the QuickCal / Booked plugin) and setting up two separate variable products - one for adult, one for child, and adding both as payment options on the QuickCal / Booked calendar. Info on how to set that up here:
View article

The above method is one of a few options for configuring quantity options in QuickCal / Booked. For more info see here: View article

If you have any questions about that, please feel free to open a ticket: