I just checked my 3 year old Inspiron 15 5577 model and no keyboard marks. If this is a real recent purchase, timeframes vary depending on what country you are in,  a return/replacement is possible. If its past the return period, talk to Dell support to see if you can get a resolution.  
Getting keyboard marks on screen which cannot be wiped off. Is little bit marks normal? They are visible from the sides or when light is hitting the screen directly. Firstly, I was not worried as I thought they can be removed, but they remain and does not go. I don't put the laptop in the bag, I don't take it outside, so there is no pressure at all. It remains pressure-free and kept with full care. Still why there are keyboard marks?
Inspiron 5301, keyboard marks on LCD screen