A term you will see in the office printing world is "5% coverage". What's that? Many printing vendors cite toner consumption in terms of "5% coverage". A typical full-page business letter is about 5% coverage, meaning that 5% of its surface contains content which needed toner to produce.
A related term is "hold-back". In commercial printing (books, magazines), you commonly see page content go all the way to the edge of the page. In the printing world, this is called "bleed". However, in the actual printing, the rolls of paper going through the printer are wider than the content to be produced. What you don't see are registration marks which are also printed to delineate the edges of the pages that will result after the paper then goes through trimmers which cut off the outer edges of the paper, leaving images which just seem to have been printed all the way to the edge. The actual printing cannot be allowed to go all the way to the edge because that would literally gum up the works, resulting in ruined output, paper jams, and a lot of manual cleaning. In the laser printer world, there is no trimming: the paper that comes out is exactly the same as went in. Bleeds cannot be effected in laser printers because toner would inevitably go off the paper edge and into the machinery. To avoid such a mess, imaging is held back from the edge of the paper, by 1/8th of an inch or so.
My experience is that using generic replacement elements in printers is gambling: they may be more trouble than they are worth. Printer manufacturers such as HP build proprietary chips into their toner cartridges, partly to get you to buy from them. Putting a generic toner cartridge into an HP printer will generally allow good printing, BUT: the printer will not be able to report how much toner is left, leaving you with no sense of where you are in the life of the cartridge. The HP printer will, on the Supplies Status page, report error Missing memory on supply, where "supply" is the cartridge and "memory" refers to the chip in the cartridge, meaning that the cartridge does not contain an HP chip because it was made by someone else.
Modern toner cartridges are equipped with sensors which allow the printer to determine how much toner is left, and report that in its web page as well as notify print servers of the level. The amount of paper and toner left in the printer represent the principal consumables in the printer, and are conventionally reported on the printer's web page in the form of a bar graph. Over time, the toner level will gradually drop as printing occurs. Eventually, the toner becomes nearly empty.
An HP printer (e.g., Laserjet P4015) will show an empty bar graph and "0%" on the main web page as the toner is depleted. However, if you then click to Supplies Status you will see the report being "Black Cartridge 1%" and "Approximate Pages Remaining: 0". Some people will latch onto that 1% value and insist that the toner cartridge is not empty, so printing should continue — but it doesn't: this causes the person to insist that there's something wrong with the print server, which has ceased sending to the printer. The reality is that a print server responds to what the printer tells it (via SNMP), where the printer should certainly be the authority on its own state. When the toner cartridge is depleted like this, there may be some small amount of toner left in the cartridge (hence the 1% value) but the amount is too small for further printing to be reliable: pages generated beyond that point could well have only partially imaged pages, with faintly produced or bare areas where toner should be. The result would be wasted paper and a print job which evaporated after producing unusable output. The printer tells the server that it is out of toner because it can no longer reliably produce output. This is not debatable: this is reality. Accept that hardware designers long experienced in the printing world have engineered their printer to say that it cannot proceed when it cannot reliably do so.