Here are the requirements and behavior for each in_bbec_type:

Q = Selected by a query that was run with the update procedure "Update Account Flag for BBEC Sync". This is sometimes known as the M2 CONSTITUENTS query.
M = Manually flagged on Account Overview.
L = Legacy, any account that was in the sync already when the types were added.
R1 = Related to accounts with type Q or M.
A = Automatically added by the sync.
S = Related to any of the above (and each other, recursively) via soft credits.
C = Related to R1.

**Q, M, L, and R1 will sync all record types. A and S will sync only core constituent tables and revenue. C will sync only core constituent tables.