How can I have the 'total purchased' select only one item?

Hello; 

Looking to have just one item selected in the form not add up several selections.  It maybe in the calculation field but only want one box being able to be chosen.

Please help.

Thanks!

If you want to only allow for one selection in a field, either limit the number selections allowed if it is a multiple choice field or us a single choice field. 

If that does not allow for the setup you are looking for, let us know which form you are working on as well as what specifically you are trying to set up and we will be happy to help.