I always mean 100% is doubled, not unstretched. It's "% elongation", not .% length".
If you're see someone say they're shooting at 400% the probably mean 400% unstretched length, because 400% elongation is a lot; probably enough to tear the bands.
If you're see someone say they're shooting at 400% the probably mean 400% unstretched length, because 400% elongation is a lot; probably enough to tear the bands.