Reading SGS 2-32 Polar Curve

I'm struggling how to read the polar curve for an SGS 2-32. It can be found on page 19 of the flight manual found he

http://www.airsailing.org/downloads/...t%20Manual.pdf

What are the two different groups of lines? I'm only familiar with one (the top set).

Any significant in a band vs. a line?

Typically the origin (0,0) is in the top left with sink rate increasing as you move down on the Y-axis. This chart is different.

What is the L/D-S=7.44 or Vs-S=7.44?

My experience is minimum sink is a vertical line at the apex. So I believe at 1020 lbs, this would be about 53 mph.

Best L/D is typically a line from the top left (0,0) origin, or about 61 mph. But again, there is no 0,0 origin and I'm not sure what the L/D-S vs the Vs-S lines are.

Any help is appreciated.

Thanks