Purchase Order does not allow for quantity calculation on specific item

I found the Order Form app under the Payment Section but it does not allow for quantity calculation for a specific item... How do I go about that?  I have about 60 items to list and I would like to calculate price, quantity and total for the entire form.

You are using the Purchaser Order payment tool, the quantity calculations are working there. Here's a screenshot during my test:

Please let us know what item is not calculating its quantity, we'll be happy to check and resolve it for you.