One option is to create a new record with each scan. Then you can use SUM
as the summary function for the quantity.
The summary function shows the sum for only the records displayed. On the computer, you can see totals for each barcode by grouping records by barcode.
Unfortunately, the mobile app does not support grouping records. However, you can see totals for an individual barcode by filtering the view for the specific barcode you want. You do have to “pull down” on the records in the mobile app to view the value of the summary function.