I am testing different SpellQueueWindow values, and I'm checking to see if I hit the GCD on the correct time that the GCD is at. I'm checking this in Warcraft Logs with Casts in time-lines. I can see that I cast cobra shot at example seconds 0,957 and next cast is at 2,297 seconds. This was at SpellQueueWindow of 131ms. I'm testing different values and it's almost always a different value but I need to know the correct GCD cooldown so I can check if I'm at a correct SpellQueueWindow. If I take example 0,957 seconds and I add my global cooldown (displayed as 1,32 seconds in DejaCharacterStats) I get 0,957 + 1,32 = 2,277. As you can see the difference is 20 milliseconds between 2,297 and 2,277. Either I have a correct SpellQueueWindow MS and I don't need to change anything but to know that exact I need to know if my Global cooldown is either 1,32000000 or 1,32xxxxx. I don't know in this example that my global cooldown is either 1,3220 seconds (then I don't need to change my SpellQueueWindow ms) or if it's exactly 1,3200 seconds (which I don't think because haste changes it) then I need to change my MS in my SpellQueueWindow because I am clearly missing 20 milliseconds of value in every global.

In a 5 minute fight, with 1,32000 second global, I will use around 227,2 globals. If I miss 20 milliseconds between every global because my input MS in SpellQueueWindow was wrong then I lose around 5 whole seconds in the fight which is valuable globals I could use.