Why do page counts not add up?
When examining the page counters using a web browser, the total number of pages displayed may be greater that the sum of the page counts from the individual trays. For example, the screen shot below shows a total page count of 4843 pages, while the sum of the tray1 and MP tray counters is 3451, a difference of 1392 pages.
The reason for this is due to duplex printing. When a two page duplex print job is printed, only one sheet of paper is taken from the tray and hence the page count increases by one. However, this paper will pass through the printer twice and hence the total page count will increase by two. The example above shows that both simplex and duplex printing is being used on this printer.