AB corresponds to the blue rectangle, and ABC corresponds to the red one.

In general, if the total number of variables is n and a minterm has k variables, then the number of cells of the Karnaugh map corresponding to this minterm is 2^(n-k). For example, here the total number of variables is 3. The minterm AB has 2 variables, so it has 2^(3-2) = 2 cells, and ABC has 2^(3-3) = 1 cell.