If the tool says 0.5%, it's "probably" about 1/2 that. They tend to indicate a chain is more worn then reality. YMMV though.

At some point, you should grab a scale and actually measure to confirm/deny the veracity of your tool. It is still a great "quick check" device. If it says it's good, you KNOW it's good.

I like to measure a 3' section of chain for better resolution when converting to %. Being 1/32" off because of parallax or other reasons is only 1/3 as bad when measuring 3X as much.
4' gets too unwieldy for me.

I use the 1" & 37" marks to avoid the sometimes problematic 'hook".
Back to reality-
Do the close visual inspection while turning the crank and describe how often, where.....
Time to leave the keyboard and look at the bike.