Hi @Vittorio

See the sma_purchase_items table as the main inventory table for the SMA system. It has a quantity column, a quantity_balance column, and reference ID columns for Purchases and Transfers columns, among other columns.
All completed stock-In [purchases, positive-adjustment (addition), transfer IN/TO warehouse (product quantity-add-up)] get added up to the product quantity in here; the same goes for all your stock-Out (sales, transfer OUT/FROM (deduction), negative-adjustment (subtraction), they get deducted from the product quantity in here.
The quantity column reflects the quantity of stock-in, while the quantity_balance column reflects what is remaining.

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Hello,

As @Enyinnaya Gift explained. The quantity is tracked using purcahse items table. The quantity file on products table is symbolic repersentation that get update from purcahse items's quantity balance value.

Thank you