Well, yes, now I see what you mean. In fact its an official GMS 1.4 bug (not sure if they ever fixed it even on GMS 2)
On 144Hz displays, it always runs at double speed. Turn on/off V-sync in settings, if that won't help turn V-sync on and use my Fast FPS Fix, press Cntrl+Alt+F2 that should half your FPS back to normal.