Adding to create total discounts

User 1 uploads a transaction report to our database that contains a list of transactions which is linked to a list of Users when uploaded. Each transaction contains a discount. I am trying to figure out how to add the total discounts that is linked to a user. Anyone know how to add values from data fields to create a total?

See if this makes sense:
https://manual.bubble.io/core-resources/data/operations-and-comparisons#group-by

And look for the aggregation called “sum”

Do i need to remove the “$” in order for that to function? if so how do i extract it? is there a regex code for that?