Trying add cost to multiple items

Hi,

I am using this form for my cake orders. I'd like to offer my customers 1 topping at no cost then charge 1.00 per additional topping. Can you please assist me with this?  

To clarify, are you referring to this form https://www.jotform.com/91958935383171?

You would have to edit you calculation manually and use the Form calculation widget to pass the value to your payment field.

Guide:https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

Let us know if you wish to set this up and we would gladly assist you.