The tracking pays more attention to the length and position of your strokes, rather than doing what you might think of as OCR on the finished characters.

Here's a tool-assised run that the TASBot run was clearly inspired by: https://www.youtube.com/watch?v=_p_UtfOmp9E - you'll notice there's no opportunity for the actual numbers to be drawn in many instances.

A Japanese language article that goes more into the specifics: http://dic.nicovideo.jp/a/tas%E8%AA%9E