If there are no outside liberties, this 6 points large eyeshape can be turned into seki. Any of the three marked points accomplishes this result.
Starting at 2-2 gives the same result, but ...
... starting at 1-2 invites Black to make the mistake of answering at 2-2. White 3 makes a bent four in the corner shape, killing Black.
If there is at least one outside liberty, Black is alive with 5 points.
Thanks to the outside liberty, Black can give atari at 4. Without that extra liberty, Black 4 would put himself into atari.
When the last outside liberty is filled, Black 1 makes 5 points in gote (deiri counting).
(As I don't fully grasp miai counting I'd rather have someone else talk about that.)
Authors