Checksum problem

Hi guys

My problem: i participate to a GP4's 1988 Hotlap cup and we use of a performance file, because we apply power penalties for podiums'places at each race.

When i see the hotfxlap report, the last part of my checksum, corresponding to "CC" is different from the others.

What's represents this checksum and why isn't the same ?

thanks for yout answers