Comment #1 on issue 2601 by [email protected]: \repeat tremolo 9 {…} should issue an error
http://code.google.com/p/lilypond/issues/detail?id=2601
I don't think it's a documentation issue (although one could list all valid repeat factors for notes with up to 5 dots: 1,2,3,4,6,7,8,12,14,15,16 [maybe more?] are all valid whereas 5,9,10,11,13 are not), but an inconsistency in the program.
