A small clearence gap between the lcd display and the aluminium on top of the phone.

Why is there a small clearence gap between the lcd and the aluminium frame of my iphone xr. The phone is just 10 days old and this is abnormal when iphone design is so accurate, which means this is some kind of manufacturing defect. For the phone is water and dust resistant, the iphone already began to settle so many dust particles in between the gap and it is so annoying