I believe we have the same desk. It's the 70.5" x 30" XL classic. I just measured the height from the floor to the surface of the desk and it's 29". Maybe I'm doing something wrong. If I raise my chair up higher so that my arms aren't angled up, my feet are no longer flat on the floor and they're dangling which is uncomfortable. Part of the problem might be my Kinesis keyboard which is raised up a bit. I have the adjustable stands on them and just lowered them which seems to help a bit. The other issue is that when I raise the seat up enough to have my arms at the right angle, my monitor is then too low even at its highest. I might be able to solve that my putting some books underneath it.

Here's what I'm working with: https://ibb.co/MGqcpxc (excuse the mess and wires)