Packaging Units are a fairly big deal in  

Every Stock Unit and every Supplier SKU has it's own Packaging Unit.  For example, you maybe buy cases of12, but sell single units online.  Two different Packaging Units would be at play.

Shown in the above screenshot are a set of options that just happened to be in one of our test accounts.

During your technical onboarding, we install a small group of common Packaging Units that can get you started.   

You can setup as many Packaging Units as you want in the Table Setup screen.

The Global default value is Single.