onigoroshi: Dame refers to areas that are neither person's territory. If dame were to be marked correctly (which maybe it should be here), then all of the upper portion of the board would be in dame.
If you look at your dame link:
White's upper-left territory is bounded by the stones D9-D8-C7-D6-E6-D5-C4-C3-B2-A2.
White's lower-right territory is bounded by the stones H1-H2-H3-G4-G5-H5-I5-J5.
Black's lower territory is bounded by the stones B1-C2-D3-E4-F4-G3-G2-G1.
Black's upper territory is bounded by the stones E9-E8-D7-E7-F7-G6-H6-I6.
The circled points are neither white's nor black's territory and considered dame.
The point marked 'a' is a potential capture by white if white plays A1 first, so black must fill this in if white plays A1, or take the A1 before white does.