In "Crossfire", Shakaar, Kira and Odo descend from an upper pylon, intent on reaching the Promenade, and Odo sets the destination as "Level 2D" (or so says the TrekCore script - I think it was changed to 22D in the aired episode). An assassin then contacts them, pretending to be Worf and claiming that he has to be given access to turbolift controls because there's another lift stuck on "Level 41" and Shakaar's lift has to be rerouted.
The assumption there is that "Level 41" would be in the pylon, because it makes little sense for it to be either in the docking ring, the connecting horizontal pylons or the central core.
As to whether Level 41 is just a designation for a certain height, or an actual accessible floor with possible rooms or other facilities... Hard to tell. But clearly the different parts of the station have their own numbering schemes, because the core is numbered from Level 1 (Ops) down and thus a Level on Shakaar's route that has a higher number than their Promenade destination would make no sense as the location of the fake "stuck turbolift".
Perhaps one says "Level XC" where X is the number when referring to core levels; and "Level XD" when referring to docking ring levels (Odo might have set 22D as a point where they'd change from a pylon elevator to another one, either for security reasons, or because the Cardassian system featured separate pylon elevators); and perhaps "Level XP" for pylon levels, or perhaps "Level XPU" for upper pylon and "Level XPL" for lower pylon. And perhaps the special letters are only needed when one moves between sections, so that trips within the core don't require the use of the letter C.
Complicated in any case... And again goes to prove that the station is really big, a veritable city in the sky. It's a miracle that Starfleet could run it with as few as 300 people during the early seasons.
Timo Saloniemi