We understand your Brother LC30373PKS cartridges did not print the approximate amount. We'd like to help. The stated page yields for genuine Brother cartridges are based on the ISO testing standards. The number of pages that can be printed with a cartridge is affected by several factors, including paper size, number of pages per print job, amount of print on each page, font size, and print content (graphics, charts, etc.). Print jobs with large text fonts, graphics, charts, and/or large amount of solid coverage (black or any given color) will use much more ink and will shorten the life of the ink cartridge. If you have any questions about your Brother Genuine cartridge, please contact Brother customer service: https://www.brother-usa.com/brother-support