You mean there are people who rely on finding documentation and don't look at the code? It never occurs to me to do that for things at this open-source non-professional level.
But really you only have to go as far as the header file to find
void write(int value); // if value is < 200 its treated as an angle, otherwise as pulse width in microseconds
Seems clear enough to me (even if misguided). The parameter is an int and 200 is limit for an angle, over that counts as microseconds.
OTOH TolpuddleSartre is also correct that, if you are using default timings then 544 microseconds is the shortest pulse it will actually deliver. But of course you can change those timings in the attach().
uint8_t attach(int pin, uint16_t min, uint16_t max); // as above but also sets min and max values for writes.
Fun isn't it!
Steve