Human meters always read lower than the pet meters, because they are intended for reading human blood which is a different composition than kitty blood. The protocols here all use human meter readings, so the human meter is used to see trends and ups and downs rather than having a precise vet machine number. You can always take your meter to the vet next time you have blood drawn and get a comparison between the vet reading and your reading. This will give and idea of what sort of differences you will see.
Some of us do use the pet meter, but the strips are much more expensive than those for a human meter and can become very pricey when you are doing a lot of testing,