DigiKey part number 1214-SST-20-WG40-A2-C8402TR-ND
The A in this part number calls out Solder Pad Type A. See data sheet snip below.
DigiKey part number 1214-SST-20-WG40-B2-C8402TR-ND
The B in this part number calls out Solder Pad Type B. See data sheet snip below.
Here is the link to the data sheet.
The A and B Solder pad types can be found on page 10 and 11 of the data sheet.