Thanks. Peter. It is the "11X 82", "231X82" and "5 X92" notations that I am enquiring about, not the 10.-, 9.- and 8.50 sheet values.
My first guess would be that that they are added to the sheets as they are printed for inventory control purposes. It would, however, be interesting to know what they actually signify, eg: perhaps "11X 82" means the 82nd sheet in the 11th print run.