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2. Quantity. How to update quantity using Check in-out.


When Check in-out entry is linked to inventory item quantity, Books Xpress will recalculate the inventory quantity every-time check in-out transaction is created. It calculates the current inventory balance based on all the check in-out transactions and automatically updates the quantity number for the inventory item.

Since all this calculation and update happen automatically, user shouldn't touch the quantity number directly. The increase/decrease inventory quantity should be done with check-in/ check-out transactions instead of number change in quantity field. If user wants to increase the inventory balance, one will create check-in transaction with necessary amount. 

Let's see more detail with some examples.
If you had 100 apples and some buy and sell happened as follows,
the inventory quantity will be changed as follows.

1. in day 1, Initial inventory
I have 100 apples in my garage.
Transaction 1: Check-in, +100 (you need to set this initial inventory)
Quantity: 100

2. in day 2, Sales
I sold 3 apples in ebay
Transaction 2: Check-out,-3 (minus means material out and the balance becomes 97)
Quantity: 97

3. in day 3, Sales
I again sold 90 in market
Transaction 3: Check-out,-90 ( will make on-hold quantity: 7)
Quantity: 7

4. in days 4, Purchase
Re-stocking! I purchase 50 from local farm
Transaction 4: Check-in,+50 ( plus means in and will make on-hold quantity: 57)
Quantity: 57

5. in days 5, Inventory check - adjustment
I did inventory check and found only 54. It seems somebody stole three apples. have to adjust the balance
Transaction 5: Check-out,-3 ( inventory adjustment and will make on-hold quantity: 54)
Quantity: 54

This transaction based calculation is typical behavior of most inventory management system and allows users keep track of all inventory movements.

If the "Update quantity automatically" option is disabled, Check in & out module will work independently and never affect inventory quantity field.