Every time it is your turn, the game engine will run your calculate_move() function, which needs to return a valid move. In "Numberplate Identifier" (mode 1), a valid move is a dictionary {'numberplate': s}, where s is a string (containing what you think the numberplate is). In "Component Recognition" (mode 2), a valid move is a dictionary of key-value pairs 'category': b, where 'category' is a category from gamestate["Information"] and b is a bounding box).
A bounding box b = [[x1,y1],[x2,y2]] is a rectangle from the top-left corner coordinates (x1,y1) to the bottom-right corner coordinates (x2,y2).