Struggling with time overlays please help?

If you anchor it at its center (0.5 0.5) then yes it will stay in the same spot and just spin in place. However it will not keep spinning forever. The overlay is only going to rotate once to the rotation number in the amount of time you set. So if you want the overlay to do a full rotation (360) in 2 seconds, the overlay will spin all the way around to 360 in those 2 seconds and then stop (ie. @overlay OVERLAY rotates 360 anchor point 0.5 0.5 in 2). If you want the overlay to continue doing the same rotations, you will need to use a loop.
So if you want the overlay to loop 5 times total, have the overlay loop 4 times. (ie. @overlay OVERLAY rotates 360 anchor point 0.5 0.5 in 2 loop 4 times).

Infinite loops do not work with rotating overlays.