Stupid nerd post incoming. This is a pet peeve from my days designing interfaces. You need to add the margin to the outer curve of a screen to make the rounded corner effect look right. The inner curve "might" be mathematically correct on the Surface Laptop screen if you go by the top margin. But since the side margins are thinner it looks wrong. You can't pull off a elegant rounded corner with inconsistent top and side margins. I would have either made the side margins thicker or the top margin smaller so they are equal so the rounded corner effect looked correct. They designed themselves into a lose-lose situation. I see this on android phones all the time. Thinness of bezels is placed above visual consistency. iPhone side bezels are wider than other phones, but they are more visually consistent and in my opinion look much better.