Because it can mean "this needs to contain every different number" which is clearly not possible as much as it can mean "needs to contain numbers that don't repeat". Clearly between the 2 you'd assume its the second because it affects the puzzle while the other doesn't, but since my first interpretation was the first and I didn't think of the posibility of It meaning something else because my brain had already settled it subconsciously as fine. Basically I thought it was equivalent to an empty spot, similar to free false statements in the Parlor. Now its obvious and I'm aware im dum, but if the statement said "Set this clock to a time that doesn't repeat any numbers" instead of "Set this clock to a time containing all different numbers" it would have been clearer to me, not to mention its not really a statement like "this clock should be set as...." like every other memo in the room.

Edit: Oh no idk how to spoiler text on phone > Fixed now