Hmmmmm, that's a very good question that I will leave for a more senior member. Do you see that line lower down that is about even with Abe's knees? It appears to me to be perfectly parallel with the line you're asking about. Is that line in some way related to the line at the top? That deserves another Hmmmmm.
Personally, I don't know. The top one appears to be raised. The bottom one appears to be incused. But they seem very much to be perfectly parallel and about the same length, which makes me think they are somehow related.