TargetFPS can not reach the specified value

[0x5143]

Because thread scheduling consumes, the RunLoop() will execute after some millseconds (for me is 10ms+) in Windows 10.(Maybe same in other OS, like Linux)
I set target fps as 15, but got 12~13 actual.

[0x5143]

I using System.Threading.Timer fixed this problem, and avoid using Thread.Sleep for milliseconds.