Inventory Lot Control locator is allowing users to add more quantity than the maximum locator is all

Log into Oracle Application R12, then select responsibility Inventory --> Miscellaneous Transaction. Try to receive 30 quantities of an inventory item into a locator with a mximum of 20. I was expecting Oracle Forms to give me an error, saying something like, "The maximum capacity of the locator is 20 and you are trying to receive 30...". However, this does not happen. Instead, it is allowed and according to Oracle, unless WMS is enabled, this will be allowed. So the functionality works fine if WMS is enabled. This does not sound right. Can someone please help? How can we change the Form (using CUSTOM.pll) to fix