Under settings change both the end number of frames to 20.
Now click the small circle in rotation X, Y, Z so they turn red.
Click on the 10th keyframe on the bottom timeline and rotate your head to the left. Your transformations should change
on the right panel. I've rotated Y to -52.5
This becomes useful when you need to adjust your weights on the model. To get a better view of what the character will look
like when it moves we can left click and drag on the timeline and it will animate as well without pressing play.