Basically, you cannot Wait for a period of time shorter than the time it takes for the hardware to process the frame.
The timer will be analyzed on the next tick (as soon as possible) and decide at that point but it always takes a minimum of one frame so at that (rather instantaneous) speed, you are constrained by the framerate.
It can be perceived as slowness if you are relying on it to do many tasks in rapid succession because they will always take one frame to do each one. If that's the case you have to manually throttle how many tasks are done per frame (more than one), based on current framerate or some arbitrary number that seems good.