This's not about "10 bit" actually.
madVR changes display mode to something, may be to "10 bit output", SVP tries to re-measure refresh rate and fails (because "full screen exclusive" renderer blocks SVP's ability to measure it) and takes "Windows refresh rate" (which is an integer value).
It this particular case refresh rate was not changed so SVP could keep previously measured value of 59.xxx instead of falling back to 59.000.