This may have to do with light coming thru the front windshield which would make the driver and front passenger side tints appear lighter. I have 20% tints on an Audi sedan with beige interior and when I saw the factory tint on the X5 in a light interior I could tell the tint was definitely lighter than my 20s. The dealer told me its around 30%, I believe it. 35% is possible, but not 20.