Could somebody tell me what the Stretch number in IK is linked to?

I am trying to make a bones of a certain size stretch to another size. And I need to know what the number under Stretch does…

If I make a bone of lenght = 10 and apply stretch=1 it gives a maximum stretch to length=324 (so the relationship is not a simple length*stretch)

A stretch=0.5 gives a maximum stretch to length=230

A stretch=0.1 gives a maximum stretch to lenth=110

Doesn’t seems to be a linear relationship…(if it was, at stretch = 0.5 it would allow a length like 162 (324/2) and stretch = 0.5 would allow lenght to go to 100)

I am puzzled because I don’t know what stretch refers to…

If someone know, thanks for reading

If I have no answer here, I will try my luck by asking at the source (blender.org :))