In Harry Potter and the Prisoner of Azkaban, Sirius and Remus have the following conversation:
“Remus!” Pettigrew squeaked, turning to Lupin instead, writhing imploringly in front of him. “You don’t believe this ... wouldn’t Sirius have told you they’d changed the plan?”
“Not if he thought I was the spy, Peter,” said Lupin. “I assume that’s why you didn’t tell me, Sirius?” he said casually over Pettigrew’s head.
“Forgive me, Remus,” said Black.
“Not at all, Padfoot, old friend,” said Lupin, who was now rolling up his sleeves. “And will you, in turn, forgive me for believing you were the spy?”
“Of course,” said Black, and the ghost of a grin flitted across his gaunt face. He, too, began rolling up his sleeves. “Shall we kill him together?”
-Harry Potter and the Prisoner of Azkaban (Emphasis mine.)
Lupin's response of "not at all" seems to imply that Padfoot is not forgiven, yet the rest of the text implies that they both forgave each other and are now friends again. What does "not at all" mean in this context then?