Those numbers are for all Z4M, and do not include any non-M Z4 Coupes - unless they've been described wrongly when registered with DVLA!
Disappointing to see so many of them sat in storage and treated as assets rather than being enjoyed as fantastic cars. The thing is, if 260 of them are hidden away waiting for values to soar, it's going to be a very long time before they become scarce enough for the values to soar.