VPIP/PFR Discrepancy: PT4 vs Poker Copilot vs Xeester from same HH file

Hi everyone,

I'm running into a confusing issue with my poker tracking software and was hoping to get some insight from the community.

I recently decided to test three different trackers: Poker Tracker 4, Poker Copilot, and Xeester. To compare them, I used the exact same PokerStars hand history file (a small sample of about 100 hands) and imported it into each program.

To my surprise, all three trackers gave me different VPIP and PFR values. The other stats are likely different as well.

For example, the values were something like this :
Poker Tracker 4: VPIP 36,11 / PFR 26,42

Poker Copilot: VPIP 34 / PFR 25

Xeester: VPIP 40 / PFR 29

My PokerStars client and hand histories are set to English.

How is this possible if they are all parsing the exact same data? I'm guessing there might be subtle differences in how they define these stats (e.g., how they treat completing the small blind, or filter certain hands).

My main questions are:

Has anyone else experienced similar discrepancies between these specific programs?

Is there a known reason for these differences in calculation?

Which software's calculation is generally considered the most accurate or the "industry standard"?

Any insights would be greatly appreciated. Thanks!

Thom