Different Form data Intervals.icu / TrainingPeaks

Hello,

I noticed that the FORM data on Intervals.icu and Trainingpeaks do not match.

Data on intervals.icu →

Fitnes: 92
Fatigue: 114
Form: -22

Data on Trainigpeaks:

Fitnes: 92
Fatigue: 114
Form: -39

I had Form -39 on Intervals.icu yesterday.

Which data is correct or why is there a difference?