RVR not moving 50 cm when it is coded to move so

Hi there,

I have both RVR and SPRK+. I code both of them to move 50 cm per second for the same amount of time (using different devices). However, RVR doesn’t move 50 cm per second whereas SPRK+ exactly moves 50 cm per second. How should I make sense of RVR’s speed? What is the unit in RVR’s speed?