Question

If committed offset is larger than the offset of client processed last message, the messages between committed offset and last processed offset

Answer 1

If committed offset is larger than the offset of client processed last message, the messages between committed offset and last processed offset;

What happens is that; in case the committed offset is larger than the offset of the last message the client actually processed.

Then what happens is that all messages between the last processed offset and the committed offset will be missed by the consumer group.