Telemetry FPS graph

I manually capped my FPS at 90 using The ASUS GPU tool. When I'm in game however the graph shows a value that's either 100 or 91 and alternates between those two every second.

Thats what the graph looks like no matter where I am. Idling in town, hideout, map. I dont understand why its jumping in the first palce, and secondly why its going from 91 to 100 when it should be capped at 90.
I turned Vsync off ingame.