How does Tangband measure Xmax?

I was thinking of buying a pair of Tang Band W5-1138SMF to use as midbass drivers for my desktop speakers.

They claim 9,25mm of xmax, but nowhere does it say if it is one-way or two-way or by 70%Bl or by 50%BL.

Does anybody know how they measure it?

I also found Omnes audio SW 5.01 that looks similar but has one way Xmax of 7mm, which is either more or less depending on Tang Bands way of measuring.