: ( 648bd)
Black gives atari at the upper edge.

:
White's block is also an atari.

:
Black has to connect, to justify his previous move.

We already know that he would be one point better, if he let White capture his two stones, instead.

:
White gives atari in the left centre, and creates some points of territory there.

Semeai Variation:

Compared to the superordinate variation ...

• Black destroyed an additional point of White's territory at the upper edge.
• White gained an additional two points of territory in the left centre.
• Black lost one point of territory in this area.

In total, Black lost two points.

White + 2 => White + 4