In the Form Builder, there should be an option like the checkbox with options field type that is instead a fillable number box. For example, If I have a field type that looks like this:

Plates

9" Divided
9" Round
10.25" Divided (by request)
6" Round
6" Silver Rim (by request)
9" Silver Rim (by request)

instead of each option having a checkbox before it, there could be a small text box where a number could be typed. Like this:

Plates

___ 9" Divided
___ 9" Round
___ 10.25" Divided (by request)
___ 6" Round
___ 6" Silver Rim (by request)
___ 9" Silver Rim (by request)

That way the person filling out the form can indicate how many of each selected product they would like. Such as in this example:

Plates

____ 9" Divided
10 9" Round
____ 10.25" Divided (by request)
15 6" Round
____ 6" Silver Rim (by request)
____ 9" Silver Rim (by request)

That would allow for forms to be made where people can request items (such as paper goods or types of tablecloths) and indicate how many of each offered item they would need.