PWM voltage out of spec

While setting up my PWM CNC spindle I noticed the longboard PWM voltage is not a true 0-5v but approx 0.28 to 4.57v. is this normal? I ended up tweaking the vdf to compensate, using a laser it probably is not too critical, but with spindle control it is.

It’s a common misconception that the voltage of a PWM signal ranges from 0-5V exactly. PWM (pulse width modulation) actually uses the length of each pulse to provide a signal that can be translated into speed or intensity. As long as the voltage is high enough to be considered a “high” signal, it will be considered a pulse by the system, and that voltage could as low as 3V. PWM is not intended to provide a changing voltage based on the length of each pulse.

I would suggest reading this article for more info Adding a spindle to your LongMill? | Sienci Labs