Distance Readings

Does anybody know why Zwift record a different distance reading to that of the Wahoo Kickr, I’ve just completed my first ride and Zwift recorded 20km but the Wahoo showed 36 - quite a difference and it truly felt more like 36 !!

Because Zwift is a virtual world with elevation changes and your Kickr has no idea about that. Ignore what distance or speed you Kickr is saying.