OK - definitely 4, so I suppose I was right setting it to 100 before.The leadscrew is an 8mm diameter, so I'm assuming everything else is in metric as well.Anyway, I seem to have finally figured it out by dividing the given step per mm by the 4 start threads - thank you everyone for putting up with me, but now I am sure I can measure any leadscrew in the future too so I can annoy you less
I have never sees a multi-threaded lead screw.
I've seen them used on machinery where fast travel time of the nut along the lead screw is needed, at reduced positional accuracy.@OP: I suggest that you post a comment or review on the Amazon web page (if that is where you bought it), informing other potential buyers about the missing "4 start" information.
Sounds like a lead screw assembly to avoid.