Once you have reached the items manage and the venue is managing to items with different catagory for example Pre-pay and Deposit.
Once both section Pre-Pay and Deposit have been created with the same Stock. You will need to click on the Bule button that is on the right hand corner of each item.
This feature allows the items to turn off if one runs out of stock even though the other still has available, this is based on the stock of the items that were set up.
To activate the feature you will need to set up the stock to what both items have, meaning if both items have a stock of 4 the category stock has to be the same of 4 but if one of the stocks has one less or more the category stock will need to be set to what is left since the feature will take in concideration that there is only one stock. The feature will indicate you how many have been sold prior to the setup.
Once you have set everything up the category stock takes affect.