info about "script ran too long"

[Jarod24]

So i've read that the Blizzard devs added a restriction on how long scripts can run.
The "script ran too long" error is shown if your code is too slow, especially when in combat.


However i have not seen much info more than that; like how much time is "too long"? Is this a flat time or are they counting operations done? callstack-depth? or... what?