Numbers mean rotations of order 2. Mirrors are represented by red lines and and glides by green ones.
Colour symmetry in the same pattern. Reflections are represented by red lines. (12), means that the colours blue and white interchange; i means the identity.
This is an example of the case stated in the fourth row of the table in Section 4.4 (Figure 12, «p2mm») in
See the same case in