During the new MSQ quest "Preservation Their Purpose" when interracting with the "Number Pad" a sentence explains to us that we can input up to 5 digits then confirm our attemp :
Select the number keys on the pad to input a combination. Enter up to five digits, then press the confirm key.

However, in Japanese we are told that we can input up to 6 digits, and when we input a combination, we can clearly see there is room for 1 more digit.
French says 6 too, Deutsch 5. I think it is worth checking, the riddle is already easy enough (you have at most 3 combinations to try if you can't make the connection between the 2 clues), no need to give an additionnal involuntary clue.