Zwift Training RPMs

Can anyone tell me what baseline crank length is used as a baseline by the Zwift training programs? When it tells you to spin at - 100RPM - that number is based on a specific programmed crank arm length. I have long legs and long crank arms and want to calculate the equivalent RPMs I should be pedaling based on the ratio between them.
Does Zwift base this RPM on a crank length of 170mm, 172.5, 175, 180???