What is the difference in gfr calculators? some tell me my egfr is 59 and some tell me its 62?

Trivial difference: Different equations will give different values but the differences are not clinically meaningful. While a breakpoint of 60 is often used to mark different levels of egfr the difference between 59 and 62 is not clinically meaningful.

Different equations: The common egfr calculator is the mdrd equations of which there are more than 30. They a accurate to +\- 50%. They are more accurate at lower kidney function 30% or less. The numbers will be a little diferent depending on which equation is used. Your kidney function is really about the same using either equation. The real question is why is your kidney function not perfect. You need an eval.

Difference in GFR: The answer to you question is that the GFR calculators give an estimated, not an actual, gfr. The calculation used to estimate the GFR is based on a person's age, sex, race, height and weight. The difference in your estimated GFR levels is about 5%, perhaps your weight was different. The only way to know what your real GFR is is to have a doctor order a 24 hour urine for creatinine clearance.