Social Security Benefits Worksheet

The Worksheet for Social Security Benefits confuses me.

1.  Why, when there are amounts on lines A,B,C and amounts from the 1040 , and the other calculations...would there be no numbers filled in on the form?  I see only lines 1 and 20 filled in, but I think lines 1 THROUGH 20 should be completed.

 

2.  Can anyone explain what the  line 8-- $25,000 reduction is about?  

3.  Can anyone explain what the line 10--$9,000 reduction is about?

 

This is sure confusing for me!

Thanks all 🙂

Christine