type

TTileDescriptionr=record
 Layer:byte;
 Tile: word;
 Mask: word;
end;

TTileDescription=record
 Count: word;
 Descript: array of TTileDescriptionr;
end;

PTileDescription = ^TTileDescription;

var

Floor:array of array of PTileDescription;
P:TPoint;

begin
 GetMem(Floor,100,200);
 P:=Point(10,20);
 GetMem(Floor[P.x,P.y],SizeOf(Floor[P.x,P.y]^));  //SizeOf(Floor[P.x,P.y]^=8. 
                                                  //Если написать GetMem(Floor[P.x,P.y],8), то
                                                  //всё работает. Почему так?
 SetLength(Floor[P.x,P.y].Descript,1);}
end;