Spells -d N and -dN as --max-depth=N, the one form the parser takes a value for: a short flag is otherwise a switch, and the depth read as a path to measure.
-d N
-dN
--max-depth=N
du's words.
The words, the depth spelled long.
Spells
-d Nand-dNas--max-depth=N, the one form the parser takes a value for: a short flag is otherwise a switch, and the depth read as a path to measure.