Page 148, problem 593, solution diagram
Erratum: White can make a seki, by playing and .
AlexanderYoshi: So this...? Seki equals life.
Skelley: Of course, Black is still alive. But without points; i.e. it is not the best way to play for White.
Grauniad: Do you mean it's not the best way to play for Black? But how can Black do better?
unkx80: No way Black can do better. But in life and death problems, the unspoken assumption is that seki equates to life. Also, the problem author may want to show what he thinks is the not so obvious variation.
Bill: How should White play after ? It's an interesting question.
To answer that question we have to know what happens when Black plays first.
If Black lives with he gets 6 points.
So White's sente in the first diagram is worth 3 points. And White's gote in the second diagram is also worth 3 points (miai). This is an ambiguous position. White has a choice between sente or gote, depending upon the circumstances. Either play could be correct.