It’s supposed to be based off the spell, not the server ticks.
Ex, mage uses blink > Rogue gouges in X amount of time after mage pressed blink > mage instantly blinks and is also gouged.
There is a small amount of time… maybe like 4 out of 60 fps worth of time to counter such moves… it is def not server tik based or else it would be inconsistent.
Vanishing blinds is another example.