This graph shows the interval distribution of articles arriving on the same news group. This means that there where 21000 events in which two articles are posted in the same newsgroup 16 articles in-between. It seems that keeping 30 open files is sufficient.
X scale is varied.
The jaggyness of the last line implies that there is little correlation between article count and byte count. This graph shows what percentage of overall article count is consumed by the top X most popular groups. The above graph shows what percentage of overall article byte count is consumed by the top X most popular groups.