Need help interpreting seemingly ambiguous text in UTS 39

[Karl Williamson via Unicode]

It says

Forbid sequences of the same nonspacing mark.
Forbid sequences of more than 4 nonspacing marks (gc=Mn or gc=Me).
I believe the traditional definition of nonspacing mark is gc=Mn.  The 
second line effectively redefines that definition to include enclosing 
marks.  Does that redefinition apply to the line above, or just to the 
second line?  It seems to me that sequences of the same enclosing mark 
would be suspicious.

Thanks