You seem to be referring to this message:

Quote: <[Okrand] said in a co[n]versation surrounding but not in the HolQeD interview that most units of measure had alternate forms [with] {-'a'} added to mean "9 times", so that one 'uj'a' = 9 'ujmey.>

It says that the information was revealed in a conversation related to a HolQeD interview, but not part of the interview itself. Furthermore, it's not stated explicitly that this is true for {cheb}, only that it's true for "most" units of measurement. But it seems sufficiently close to what you stated that it must be the origin of your slightly erroneous statement.

De'vID