I'm having trouble interpretting the graph on p. 239 figure 7.9. Can someone explain the graph to me?

Why did he label the horizontal axis with "1-BB hand" and "1-SB equity"?

Is EQ(hb) BB's equity with hb vs SB's river range or SB's hc range?

The book says hc = 0.7 but the graph shows that hc = .767

Shouldn't the difference between hb and hc be the same on the x axis as the y axis?