I found a message on the chalkboard. Does it mean anything?

[Ninmir]

I found a very faint note on the blackboard in the Outside Room Classroom. It says, "In a timely manor". Does that point to another mystery?

[amoe06]

My best guess might be the final exam which needs to be completed in 30 minutes irl time

But it could also be a play on words, the actual saying is "in a timely manner" so manor being used here most definitely refers to the house, so maybe something happens when all "tomorrow" rooms are placed?

Bigger Spoilers if you haven't gotten very far (ie after room 46 stuff)
There are also a lot of time based puzzles in the game, the final exam being one of them. We also know time plays a role, with many clocks frozen at 1;30, with many secret events locked behind this time, the clock tower sanctum key, as well as another secret key in a different puzzle.

[TangoBunny]

I'm fairly sure it's a reference to the game's intro.

There's a vinyl recording where it says something like "the gift of the estate will be void if it is not solved within a timely manner" which makes it sound like you have a time limit.

This message is just to say "it was actually 'timely manor', because the manor changes each day, so there wasn't actually a time limit, you just have to find the room inside the manor itself."