Num Msgs	Number of messages sent to the list by the contributor during the period
% Msgs	The percent of list messages sent by the contributor
Num Lines	Number of lines in message bodies contributed by the contributer during the period
% Quoted Lines	Of the contributor's message lines, this percentage appear to be quotations from other messages
Avg Size	Average body size of the contributor's messages, in bytes
Zed	This approximates the contributor's number of messages per day, based on a standard 30-day month
Que	This is a measure of the contributor's overall amplitude on the list during the reporting period
User	The contributor's address, slightly obfuscated

Past statistics by month are occasionally posted HERE.