Gari Merrifield9,548 Points
At about 3:50 in the video, Guil says that 80% 50% moves your viewing position the top right...
80% on the X axis, horizontal position, is to the right, but 50% on the Y axis, vertical position, is not top, but center. Just a minor point of clarification. ( I point this out because it confused me when it was mentioned, so I watched it a few more times, and then reviewed the MDN docs to get a clear understanding )
Steven Parker162,979 Points
The forum is a great place to get help from other students, but may not be the most expedient (or even certain) way to contact the staff.
The recommended way to report bugs is described on the Support page. If you're the first to report one, it might get you a an "exterminator" badge.