interpet a graph

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I scanned a face ( inside to outside) on a part. I check it 4 places 90 degrees apart. Then checked the straightness on them with the graph. My question is, what does the green line tell me on the graph. 2 of the graphs have it to the left of the graph and the other 2 have it to the right. Would this be the start of the scan or what. Like I said, I started all 4 scans on the inside of the face so wouldn't they all start in the same direction if that is what the green line means. Also what does the "X" "Y" and "Z" lines tell me. We are just starting to use the piweb reports. (see attch.) Thanks in advance

grapksDoc1.pdf