The human meters, on the average, test about 30-40% lower than pet meters. This data comes from international feline diabetes expert Dr Rand of the University of Queensland who obtained hundreds of paired tests when doing studies of feline diabetes. She observed the human meters reading an average of 30-40% lower values values and noted it in several of her research publications.
If you recall from your basic school studies, you get the average by summing up all the test scores, then dividing by the number of tests. There will be some tests higher than this average; there will be some tests lower than this average. (Well, unless everyone gets the exact same score!)
When you compare the difference between any 2 meters, the difference between them when using the same blood drop will vary, even at the same glucose level. Part of this is because the meters sold in the US are allowed to test as much as 20% lower or higher than what a lab would get.
Calculating the +/- 20% for Dulce:
The AT test of 72 means her glucose was somewhere between 57.6 to 86.4.
The EGP test of 54 means her glucose was somewhere between 43.2 to 64.8 .
The 2 meters could be as much as (86.4-43.2) or 43.2 mg/dL apart, or as little as (67.8-56.6) or 7.2 mg/dL apart, depending on whether each meter was reading high or low or someplace in between.
The EGP could be from 50% lower (1-[43.2/86.4]) to 18% higher than the AT value ([67.8/57.6]-1).
The AT could be from 100% higher than the EGP value ([86.4/43.2]-1) to 11% lower than the EGP value (1-[57.6/64.8]).
Calculating the +/- 20% for Badgar:
The AT test of 377 means his glucose was somewhere between 301.6 to 452.4.
The EGP test 331 means his glucose was somewhere between 264.8 to 397.2.
The 2 meters could be as much as (452.4-264.8) or 187.6 mg/dL apart, or as little as (397.2-301.6) or 95.6 mg/dL apart, depending on whether each meter was reading high or low or someplace in between.
The EGP could be from 41% lower (1-[264.8/452.4]) to 32% higher (1-[397.2/301.6]) than the AT value.
The AT could be from 71% higher (1-[452.4/264.8]) to 24% lower (1-[301.6/397.2]) than the EGP value.
Using just 2 pairs of tests (4 total tests) and the +/- 20% variance shows that the possible differences may vary widely.
The research Dr Rand did with many more tests narrowed down the average percent difference.