PCM Diagnostics & Tuning - EFIlive speedometer calculator: How accurate?

I was wondering how accurate the Vehicle Speed Sensor Pulses per Mile is, so I input the stock tire size and rear gear (245/50/16 = 25.65" & 3.23) and came up with 101588 and a Trans Output Shaft Revs/Mile of 2539. Then I pulled up the stock tune and it reads 104612 and 2615. That's a 3% difference, hardly enought to lose sleep over, but certainly enough to cause trans calibrations to be off. Any thoughts on this, or is not worth bothering over?

sometimes i have noticed that if i put in the number and do the calculation and then click calculate again it will change...... maybe efi live might want to check that out.. haven't had to do it lately so idk if the latest update fixed that