I have a logic problem (knights and knaves) I need help with?

Okay if your familiar with logic and you know of the knights and knaves problem I can really use some help. I know knights tell the truth and knaves lie. I know that if there are two people A and B and A says, “At least one of us is a knave,” and B says nothing A is the knight. Example:
A B
knight knave true
knight knight false
knave knave true
knave knight true

Because of A’s statement one of the two has to be a knave so they can’t both be knights so logically A is right.
Now this is where I get a little confused:
A says, “I am a knave or B is a knight,’’ and B says nothing. How is it possible they are both knights?

P.S I missed class when this was taught and I won’t be able to contact my lecture or anyone from class because the semester is over. Can someone please explain the answer I was given in the notes I received for the second part and shed a little light on logic.