The Canon MP495 cannot physically see inside the cartridges to find out how much ink is actually left. Instead, the copper contacts on the outside of the cartridges contain this information. The ink levels start at full, and for every page printed, or every head cleaning routine completed, the printer writes this information to the cartridge. Eventually, the cartridge will state that it is empty, however this may not be the case, and it may be possible to use the remaining ink in the cartridge.
If you have refilled your cartridge, or have purchased a remanufactured one, the copper contacts will already hold the information that the cartridge is empty. Clearly they are not, but it is not currently possible to reset the ink level information on the copper contacts of the cartridge.
Instead, you simply need to override the empty error message that is being displayed using the “stop / reset” button on the printer.