Hi,
from the manual I stored, 5.14 Search Depth paragraph p. 36 (thus a different version), I quote: "The search depth for these
certain moves, the Shannon-B Strategy, is not displayed. It can be up to 10 or more half-moves."
Hence it could reach 32, the stated limit, even with "only" 21 half-moves of Shannon-A completed search.

Sorry, I don't keep track where from did I get this manual. Anyway should you like to get it, I uploaded it here.
MfG,
Eric