1) Piece placement: there are two parts
a) * piece placement: similar to chess. Use x/X for dark Jeiqi piecesb) * captured pieces: all revealed captured pieces and their numbers, enclosed by brackets []. This part appears immediately after the first part, without any space. Pieces with no capture are ignored. Jeiqi pieces are not compulsory since we can calculate them from the board and revealed captures. That can make the FEN string a bit shorter, avoid redundancy and inconsistent data, avoid ugly using due to 2 -digit numbers (Jeiqi pieces could be 15 - two-digit numbers). Empty brackets could be omitted too. Pieces can be placed in any order. For being beautiful, it is suggested to list all-white pieces first, descending by piece values.
Example of a capturing record:
