How can I count the number of boxes selected with the Appointment Slots widget?

I'm selling 4 ad slots each Monday. I'd like to calculate how many selections are made and multiply that by the price of each ad to have a total for payment, but I am unable to get a total of checkboxes without individually testing the condition for equaling each date.

I also tried the ticket widget, but I could not find in that widget where to assign the price. I did not see how that widget was different from the appointment slot widget. 

https://form.jotform.com/82215218784964

Hello,

It is not possible to sum up the options of Appointment slots or similar widget. However, I can suggest to use Inventory widget for every option and to calculate the total with Form Calculation widget:

Please let us know if you need more help with this.