Question about classification

I read a couple of papers about stellar classification in 
which classification results were reported not in terms of
error rate, as it is usually done in classification, but 
instead in something like : classification accuracy is 1.6
subclasses.

I don't think I fully understand this system.

Does classification accuracy of 2 subclasses means that all 
objects were classified either correctly or with neighbouring 
class ? Not a single object was classified with a different, 
completely randomn class ? I find it hardly reasonable.

And what about accuracy of 1.6 subclasses ? Does that mean that 
40% percent of the objects were classified correctly and 60%
as their neighbours ? Once again, not a single object was 
classified absolutely randomly ?

Thanks a lot.