If the whole exercise is not fitting on the screen, please scroll down and click on the full screen button in the bottom right-hand corner of the exercise. The full screen button looks like a rectangle with arrows point to the corners. Once pressed it will expand the exercise to fill the screen and make best use of the screen's size.
If the full screen button is not visible then the problem is that the browser's zoom is set higher than 100% and is cutting off part of the exercise frame. Please follow the instructions below for the correct browser to set the zoom to 100%.
Safari (see “full page zoom”): https://support.apple.com/kb/PH21489?locale=en_US
Links updated May 24 2017