To calculate the movement error:
E = D2 / D1
Where:
E = Error
D2 = Distance the carriage actually moved D
1 = Distance the carriage was requested to move
To calculate the corrected setting:
C = Z * E
Where:
C = Corrected Z-Axis mm/rev
Z = Z-Axis mm/rev from the test
E = Error
*Taken from the meticulous z axis instructions