The waste pages are calculated from last time the supply was collected after the supply was replaced in the printer.

 

As JetAdvices from collect the printers every three hours, it will never be an accurate number because you could have 500 pages left the last time JetAdvice collected from the printer. Then the customer could print a big job which will empty the supply before the printer is collected from again.

Then, the customer replaces the empty supply and next time JetAdvice collectscfrom the printer, the supply has been replaced with a new supply.

Now JetAdvice will show the 500 pages as waste pages even though the printer has used the whole supply but this is as accurate as it can be.

 

So waste pages in Jetadvice for a used supply is indicative of how many pages are left in the supply and it can never be 100% accurate.