Discrepancies In Measuring strain

Hi folks,

I have been struggling to get good strain rate lately or maybe I think I am?

So what I usually do is this:
Measure bpfsl: ~17 cm
Heat the penis for 5 minutes (in flaccid state) and measure again:
Bpfsl: 17.5 cm

Do my hanging routine:
10 min cool
1 hr heated
10 min cool

Measure bpfsl: 17.5 -17.7 cm

Using pre workout heated measurement and post workout cooled measurement,
Strain = 0-1.2%

Even though when I measure inside the vacuum pump while hanging, I get strain rate ~6%.

Today i thought let’s heat it flaccid for 5 mins and then measure. And voila I got

Bpfsl post workout heated: 18 cm -> 2.9% strain rate.

So what’s my actual fatigue rate? <1.2% one or ~3% .

Also why this strange experience? Anyone else experiences something similar ?