The car needs to be fully up to temperature. Needle firmly on the 90 for at least a few minutes. It will only ever be an estimate based on what the ECU 'THINKS' is happening. Doesn't account for hardware issues correctly, so take anything you get numbers wise with a huge pinch of salt.
Personally i would be more worried about logging boost, fuelling, timing etc. to see if the remap is safe and half decent, rather than worrying about estimated numbers