How can I disable customers from changing the value in the payment fields?

Good Day, 

On the registration form I use for kickball, the payment filled allows customers to change the value. That's not suppose to be. The same form was used for my

last kickball session in 2017 and customers weren't able to adjust the amount. 

Can someone please give instructions to fixing this problem?

Here's the link to the form: 

https://form.jotform.com/71970651684162

You can also go to www.platinumplaysports.com , click the registration tab towards the bottom of the page and begin to fill out the form. You'll that $75 populates into the payment field, however, you are able to change the amount. This is causing a major problem. As some clients have started to adjust the amounts when they're not suppose to. 

Hi

At first select calculated field and click widget settings.

Click "..." button.

Then select "OPTIONS" on right side bar and check "Result field is read only".

Click "BACK" and then click "SAVE". If you don't click SAVE, your changes will be discarded so please don't forget to click SAVE.

If you have any further questions let us know.