Ok the problem I seem to have is when I put it to full screen things start to speed up.
Here's an example.
I have a private variable for a shot timer. set to 0 at default.
I also have a private variable called Shot Time set to 20.
I have it so every tick add 1 to shot timer, and a separate event saying when shot timer is greater than shot time, it spawns a bullet and resets shot timer to 0.
When on full screen it fire exponentially faster.
Well I set it so when increment the shot timer by 1 * TimeDelta it fixes the issue.