If you want to deduct ingredients from your 'Inventory' on brew day, go to the desired recipe and click 'Brew'
On the next page, after clicking 'Brew', scroll to the bottom to see 'Inventory Deductions'. Click the top check box to select or unselect all items;
Click the check box for an individual item to select or unselect that item;
See: Total inventory quantity, recipe quantity and resulting quantity.
Once you click 'Brew It', the selected Inventory Deduction has been executed.