mysterious syllables

[Georg von Simson]

I am still struggling with my edition of the (bhikSu-)prAtimokSasUtra of
the sarvAstivAdins. In this connection I have the following question: In
some (not all) of the manuscripts (from Central Asia) there appear
sometimes (not always, and mostly in the first part of the text and for me
quite unpredictably) at the end of a rule, usually after the number of the
rule, one of the following syllables:

     a, azr(A?), kau, ni, ra, rA, rAH, vai, zraH, zrA, zrAH, sa, sA.

Has anybody an idea what function these syllables might have?  Is this
phenomenon known from other mss.? The prAtimokSasUtra is a law-text, where
one would not expect mantras or magic. But: these syllables are clearly not
a part of the main text; they might have to do with the writing or with the
recitation of the text? In the large collection of the "Turfan-manuscripts"
these syllables do not seem to appear at other places, but just in this
text - created by the scribes only to annoy me? :-).

Georg v. Simson