Created Condition to calculate values

Hello, I calculated values from one question and wanted them to post in my payment section of the form.  

Condition: If 15.Class State: Is Filled

Do: Copy a fields value

From: 15. Class

To: 18. Register for Classes and Membership

However, when I fill the form, the values are not placing in my product quantity text box. 

I am assuming that you're referring to this form: http://www.jotform.us/form/73457684284166

Just to clarify, are you trying to pass the number of the selected option to the payment total?

For example, if the user selected two option in the Class page.

Then the number of classes should be equal to 2 and the total amount should be $100.00.

Is that correct? If yes, please let us know so we can assist you properly. 

Yes, that is correct.

Please do the following:

1) Delete your condition.

2) Add a Form Calculation widget: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-Your-Form, and hide it: https://www.jotform.com/help/434-How-to-Hide-Form-Fields 

3) Perform the following calculation: https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget 

4) Pass the total to your payment field as shown on this guide: https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field 

Please test my clone version of your form: https://form.jotform.com/73468729626976 

See the result:

You can clone my form and use it if you want to: https://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL 

Let us know if you need more help.