The site uses the (a) and (b) subletters to help identify variations within the checklist. Many sets throughout the site have them in various ways.
For this particular set, it was released with base variations, which then the cards are issued subletters. These subletters are not physically on the cards. When used correctly, the (a) and (b) subletter procedures (and sometimes, many more letters are used) are the way the system can track these variations in the collection summary. For this set, it looks like the basic set is 1,000 cards and the master set is 1,276 cards.
The subletters should not be in the number field. They should be moved to the subletter field once the Note and Note2 fields have the proper VAR structure.
Some sets have not had the subletters migrated from the number field. Please submit an IR to report any sets for this adjustment.
I hope this makes sense. Thanks, Brian
I am one of the members that helps within the site. I work closely with the IRs and can answer most questions. Please send me a message if there is anything I can assist with. If I don't know, I can certainly try to figure it out or direct you to a resource.