Definition for end of SKUs

Anyone know what the last two letters of the SKUs stand for?

For example; AS, AT, AU, AV. All four of these SKU numbers are apart of Adobe CLP4 & CLP5 Contract types. But do the initals stand for something? 

Current thoughts for other initials are: AT – Term license, or AU is and upgrade? AS is a site license?  AV is a VIP?

Could someone please send over a document that explains all of these. Thanks!