I planned to put together an entire write-up and video for you, but I've run out of time tonight and I'm not sure when I'll be able to finish it. (Hopefully tomorrow night.)
The tl;dr until that happens: between 1000 and 2399 the timer displays dashes, yellow digits (as opposed to green ones), and sometimes nothing at all in the hundreds' place of the timer, because the game thinks the "hundreds' digit" of the time is higher than 9 and so it searches for the appropriate higher "digit" in the internal graphics file past where it is supposed to look. (The tens' digit and the ones' digit of the timer always display normally.) Above 2399, the game runs out of "digits" in the graphics file to use, and it starts displaying garbled mash-ups of multiple graphics that are sometimes legible - though nonsensical - and sometimes total nonsense. (There are some peculiarities about this behaviour that I want to investigate further.) Above 3499, the game stops coming up with new garbled mash-ups for the hundreds' digit every 100 seconds and instead starts using the same one for every time higher than this. Above 32,767, the timer freezes and won't tick down - making the level effectively untimed - though the game will still display the time (complete with garbled hundreds' digit) and it will still award you time bonus points. More on all this stuff hopefully coming soon.
The tl;dr until that happens: between 1000 and 2399 the timer displays dashes, yellow digits (as opposed to green ones), and sometimes nothing at all in the hundreds' place of the timer, because the game thinks the "hundreds' digit" of the time is higher than 9 and so it searches for the appropriate higher "digit" in the internal graphics file past where it is supposed to look. (The tens' digit and the ones' digit of the timer always display normally.) Above 2399, the game runs out of "digits" in the graphics file to use, and it starts displaying garbled mash-ups of multiple graphics that are sometimes legible - though nonsensical - and sometimes total nonsense. (There are some peculiarities about this behaviour that I want to investigate further.) Above 3499, the game stops coming up with new garbled mash-ups for the hundreds' digit every 100 seconds and instead starts using the same one for every time higher than this. Above 32,767, the timer freezes and won't tick down - making the level effectively untimed - though the game will still display the time (complete with garbled hundreds' digit) and it will still award you time bonus points. More on all this stuff hopefully coming soon.