OK, we may have a breakthrough.
@ronlawrence3 and @Frank_Wiebenga would you guys both be willing to give
A try?
Basically just press Retract All → Extend All then 1,000mm of belt (measured by the white part showing, length is 0 when fully retracted) will extend and can you measure that belt with a tape measure?
It will be slightly more than 1,000mm because of a little overshoot but it should be like 1009 or something like that.