I will stick my neck out here. I saw an earlier message where you were having some difficulties with gnus, gmail and message counts.
If I understand you correctly, you are trying to archive some Gmail messages from your gnus Gmail group into nnarchive groups. I think you want to: First, copy the messages you want to archive from the Gmail group into your nnarchive group. Second, in your Gmail group, delete the messages you wish to archive by moving them into the group "Gmail/[Gmail].Trash". This makes sure that Gmail actually removes the messages.
