Add Buy in Multiples to a Item Product

Products>File>Items>Insert 

If this item must be purchased in a specific quantity, enter that quantity here. The program will automatically notify you with a warning message if the purchase order does not agree with this quantity. If you want the program to ALWAYS correct your manual entry to agree with the Buy in Multiples quantity without a warning message, then set Automatically Resolve Buy in Quantities and Sell In Quantities to Yes.