Total Discrepancy is the total difference between all lost & damaged, found, from holding, and reimbursed.
0 means you have already been reimbursed.
A negative value means either:
you were reimbursed more than once for the same item
there is a gap in data and an item was lost/damaged before the data starts, but there is data showing items were found
Amazon counted one or more "From holding" transfers as a Reimbursement - In other words, they sometimes say "Transfer from holding account" on the Inventory Adj report and there is a "quantity-reimbursed-inventory" on the Reimbursements report, but not always. It seems to depend on the situation.