grid numbers refer to the chess board. the squares are set up on an algebraic grid system so that players can know where a piece is located or where to move it to. When you are looking at the chessboard from white's perspective, the bottom left corner of the board is a1. The squares go up in number as you go vertically up the board. So the squares above a1 would proceed a2, a3, a4 etc. As you go horizontally across the board, the letter reference goes up in sequence. So the square to the right would proceed b1, c1, d1 etc. You can check any beginner book on chess for a more visual example. This system of labeling is used as a universal language for charting moves so that chess games can be recorded and shared worldwide.
I dont understand what the grid numbers mean some one help thanks