It is indeed math, you have to calculate it.
Often the servo position is updated every 10ms or every 20ms. That makes it possible to control each servo motor independent. If the speed is set faster than the servo motor can do, then it will be behind a little and nothing bad happens.
Do you know the maximum speed of your servo motors ?
I made an example a few weeks ago (click on the start button in the middle-upper of the screen):