The Striking window serves one purpose during ringing and another afterwards. Its content and appearance change accordingly. Also, it is only useful if one of the bells is being rung by a person. If the computer is simply ringing by itself, or it is being used for silent practice, this window will have no useful content.
The above image shows the window after ringing has finished. It presents a histogram of the striking results from the touch just rung. The line up the centre of the window represents perfect striking. Columns are drawn either side of this line, dividing the ringing into categories every 25% of a blow, early (blue) or late (red).
Good striking will tend to concentrate all the blows in the middle (as in the above image). In that case you can expand the central portion of the graphic to fill the screen and see a more detailed breakdown:
The "vital statistics" of the performance are shown at the top distilled into a little bar graphic and two numbers: the mean and the standard deviation (roughly speaking, two thirds of the ringing lie within the standard deviation bar). Ideally, the mean should be close to zero and the standard deviation should be as small as possible (a figure in the 30s is very good ringing). The overall figures are further split into handstroke and backstroke.
Here is the "By Position" statistics for someone who is attempting to ring the treble to plain hunt on six bells, but is failing to reach the back most of the time:
And here is the "By Bell Followed" figures for a ringer who is ringing the treble to major quite well (evident by the thin bars), but is relying too much on ropesight and is striking too close to the bigger bells as a consequence:
Blank speaks for itself. Turning the screen blank during a teaching session can sometimes be useful if the student is focusing too much on the screen and neglecting to listen.