A convex curvature of the CTX 3030 screen may be noticeably different from one machine to another.
Some variation in curvature is a normal part of the design and process when creating a watertight and water pressure resistant structure and is well within tolerance. It will not affect the display and should not affect your detecting experience.
As always, should you have any concerns with your Minelab product, please contact the Customer Care Centre at your nearest regional Minelab office.