TC / SE Strategy session 2 and 3

GRE Verbal Problem Solving
1

Confused with a couple of of the contrast / support words that I came across while I was going through the TC / SE strategy series session 2 & 3
The words are " could be and could have ".
I remember could be being “Equal to” as explained by Greg during session 2 of TC strategy
and "Could have " in the Logic word list that means “NO”.
I am unable to wrap my head around this as it changes the logic completely .
I might just be overthinking but it’d be great if you could help me out here !

Thanks

2

Can you give some example sentences where this appears and we can try and figure it out