Adding Items in field and then subtracting them from another field

[Grant_Gray]

Hi peeps

I am new to Airtable and am starting to get the hang of counts, etc which I use to add up the number of items in a field. The fields are a form completed that will drop in a linked field from another table. I can add those up per row and get a sum per user like so:

Each line is the completion of a form by a user with them adding their details each time. What I want to to now is either change the form to:

A. add the same item to a user to create one line and one total
B. subtract the sum of all the items the user added from a set total

So if there are 50 items and they have gone in 3 times and chosen 15 over the 3 times, the total would reflect as 35 somewhere. This can be a single row or at the top of the sorted list, I dont mind. We just want to get all users to complete all tasks.

Does anyone have any suggestions? Open to linking the users from another table if that helps.

Thanks

What I want to do now is add