This plot shows the absolute value (distance from 0) left on the tape at the end of the match.
The default view shows all tape lengths, with the values being averages over all the opponents, and both sieve and kettle polarities. You can select a single opponent to focus on from the "Opponent" dropdown, or show the polarities separately by checking the appropriate box.
Clicking a row switches to an alternative view, which shows that particular tape length, both averaged and against each opponent, simultaneously on one screen. In this view, you can also toggle polarity (between averaged, sieve or kettle) by clicking at the underlined words in the plot title. Clicking on a row returns to the original view, showing the opponent on that row.