Digital BW, The Print

So, I'm sitting here wondering how a cart I just installed, about 2
weeks ago, in my 1160 is complaining that the ink is low when a cart I
installed a month ago in my 860 still reads more than half full.  I
would certainly understand the discrepancy if I had been printing
anything larger than 8.5x11" on the 1160, but I haven't.  The truth is
that I have put maybe 50 prints through the 860 and 30 through the 1160,
all 8.5x11.  Is the print counter in the 1160 flawed in that it doesn't
account for print size, or is it something else entirely?  What gives?

Any insight appreciated,
Daren

PS. It's my understanding that the print counter DOES NOT account for
ink coverage, is that true?