kV × volts = unloaded RPM. Enter any two — the third solves. Latest two entries win.
A prop-loaded outrunner typically turns 80–90 % of its unloaded RPM; that band is a rule of thumb, not a spec. Measure the real number with Prop Tach and read the factor off the third row. kV itself is defined unloaded, so the implied kV is only honest if the shaft was bare.