How does Compiere decide which location the inventory is going to be pulled from when an order is entered?

It appears to pull the inventory first from the locator setup in the Product Screen (the default location), then it appears to pull inventory based upon the order in which the inventoried was received into stock.

The Warehouse and Locators screen allows you to set a relative priority.  If I assign a high relative priority to a locator, is everything in the locator set for that realtive priority.  I assume it does, but how does this relate to the "primary" locator setup in the Products screen.

Thanks in advance,