There is a lot of confusion on this topic.
Here is a quote from SIMONK on RC Groups forum on this subject:
"Hmm, I'm not sure what software they are actually using there, but I think in general, it's perhaps easier to just set the min/max on the flight controller than to try to go through and calibrate all of the ESCs. Calibration is fine, though, and it should work if you do them all the same -- but calibration in itself is not a precise process, since it has to inject margins to deal with what normally calibration was used for: deviations in oscillator speeds with temperature, stickiness in the sticks or trim, etc.
If it is using my stock endpoints, I usually just use something like this (naze32):
set minthrottle=1064
set maxthrottle=1864"
If you look at the SimonK firmware flowchart it doesn't even support calibration unless it detects PWM input mode. If you use Oneshot125 it uses the stock endpoints.