Your page only mentions > Upper bound estimate of possible legal chess position (counts en passant, castling, sides to move, allows underpromotions): 8.7E+45.

Your page only mentions > Upper bound estimate of possible legal chess position (counts en passant, castling, sides to move, allows underpromotions): 8.7E+45. But how exactly is this number determined? Is this a sampling based estimate? My 8726713169886222032347729969256422370854716254 is an exact upperbound on the number of so-called urpositions, and is not sampling based. In any case it will be easier to continue this discussion at https://github.com/lechmazur/ChessCounter/issues/1 https://github.com/lechmazur/ChessCounter/issues/1