Thanks for clearing up everything about the number dial!
Some other things I noticed:
- On the piano, the keys are labeled with numbers in the range of 1 and 6, but in the number selector GUI you can select numbers up to 10 - that's kinda strange.
- I'm not sure if this can be fixed, but if you close the piano your characters's texture appears before the disappearance of the image of the keys.
- I got a call from P. in Room 2 regarding the piano puzzle even though I have already completed it - this event did not occur in my first "playtrough".
- I couldn't open the menu using the Esc key after getting caught under the bed in Room 5.
And a suggestion: I think it would be cool if the staff members started "banging" on the door if the player chooses to close it (after hearing an enemy nearby).
EDIT: Oh, I just realized I didn't answer your quesiton. It took like 10-15 minutes of walking around randomly the entrance trying to find a key or a hidden switch to open the door - then I realized I'm dumb as hell.