The idea is that if you measure a table, you will want to know the details of its surface. Whereas if you measure a TV set, you might want both the physical width and the diagonal screen size, not counting bezel
If you measure the slant, the top part of the laptop might not fit in the sleeve. Including the screen within the measurement is of utmost importance to get the measurements just perfect.Normally, laptops are two inches tall or less than that. Again, you can convert the inches to ...