I am not sure if an answer can be given to this problem because you can never determine the number of moves in a match. There are moved in which some of the pieces would be killed, but there are blank moves as well (in which no piece is killed, and in which the piece moved forward and then moves back). [Argument A].
However, if just going by the fact that the black pieces have moved 4 times less. Thus white pieces have not-lost 4 more matches than the black pieces. Thus black pieces might have won some number of matches (and from Argument A, we would never come to know of that number).
Please also note that a win (for black pieces) or a draw (for either black pieces or white pieces) can happen in an equal number of moves in 1 match.
Thus if both play 100 moves each, the black pieces have the last move, and they draw or win. White pieces dont win for sure in this case.
When white pieces draw or win, they would have played one extra move. So in case of black pieces not winning. Thus, the cases of white pieces win/draw is 5.
From this we can't make out how many of those cases were draw and how many were wins for white pieces.
Also, from Argument A, we can't figure out the number of matches - coz its different in each match, and there's no higher or lower limit on the number of moves per match.
Hence I'd assume this question cannot be answered.
Anyone with a greater insight into this one?
Who says elephants can't dance?