How to tell a Scratch from a Crack in a Cylinder?

All Clean, Ready to Assemble. Did a Final Hone with a Flex-Hone
and Saw This Line at the Bottom of Cyl 6... (on a 273)
It is Perfectly Straight, up/down.
Ran the Stone-Hone thru it One-More-Time and it was Still There!
I can't feel it... but I don't have fingernails (just nubs)
The Flex-Hone cleans up the lines left by the Bore Gauge but not This Line.
How do I know if I should just Stop? I tried to do a Budget Build at Home w/ No Machining...

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You might want to consider getting new stones, I don't mean to sound disrespectful but that honing job doesn't look good, needs a better crosshatch pattern.