I am puzzled i didnt think it was a level?
Why? Did you think there might be a gap in the space/time continuum?
If cleared, you can fly at any level you wish. FL415 would probably be acceptable if there was no other traffic at 41 or 43.
Same sort of confusion existed when we first started giving out FL300 post RVSM. Pilots soon got the hang of it when they realised their a/c didn't dissapear up it's own contrails when they levelled off at that level
VL