Page Yield not enough for HP 12X Q2612X toner
The page yield is at 5% page coverage. Toner use is by how much toner is placed on each page printed and how many you print. Depending on your printer make, model and toner cartridge size along with toner coverage per page, determines how many pages you'll get out of it. If you are printing photos your page coverage is close to 100% and the number of printed photos will be much less than the amount the number of pages you would be able to print if you were just printing standard text documents.
Toner page yield might not be exact, even original OEM toners will have this issue, but don't worry if the print tell you is out of toner soon or toner life end just reinstall and continue to print until the print start fading out.