what are these line marks? It’s aluminum frame and shop says it’s from factory but could it be defect?
That could be a lot of things. If that frame is new, most likely it wasn’t up to spec and they had to remove some material.
As that’s a metal frame, I wouldn’t worry too much about it. They can take quite a bit of abuse, and some minor scratches are no issue - unless maybe you want to try a carbon seatpost.
If that was an expensive frame, maybe get in touch with the manufacturer directly, if the shop doesn’t help
From experience, lines on aluminum frames are often just cosmetic — they can come from the extrusion die, bending the frame, or brushing/polishing at the factory. If the frame isn’t bent, cracked, or weakening, it’s usually fine. You can ask the shop to confirm if it affects structural integrity, but most of the time these marks are purely visual and don’t impact performance.
The important surface is at the top where the clamp is. The rest of the seat tube surfacing/smoothness is mostly irrelevant, unless it’s so bad your seat post won’t fit.
(and having had a seat post get pretty stuck in the seat tube one time, having the inside of the tube not perfectly smooth (=less surface area in direct contact) might be a good thing)