Large database tables on a multisite setup

I have a wordpress multisite setup with many subsites. Some of these have the Top 10 plugin activated.

I was under the impression that the plugin uses two database tables for every subsite:

• wp_blogid_top_ten
• wp_blogid_top_ten_daily

But on a multisite setup there are also two global tables: wp_top_ten and wp_top_ten_daily.

mysql> describe wp_top_ten;
+------------+--------+------+-----+---------+-------+
| Field      | Type   | Null | Key | Default | Extra |
+------------+--------+------+-----+---------+-------+
| postnumber | bigint | NO   | PRI | NULL    |       |
| cntaccess  | bigint | NO   |     | NULL    |       |
| blog_id    | bigint | NO   | PRI | 1       |       |
+------------+--------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> describe wp_top_ten_daily;
+------------+----------+------+-----+---------+-------+
| Field      | Type     | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+-------+
| postnumber | bigint   | NO   | PRI | NULL    |       |
| cntaccess  | bigint   | NO   |     | NULL    |       |
| dp_date    | datetime | NO   | PRI | NULL    |       |
| blog_id    | bigint   | NO   | PRI | 1       |       |
+------------+----------+------+-----+---------+-------+
4 rows in set (0.01 sec)

What exactly is stored in the wp_top_ten_daily table on a wp multisite setup? The table currently has over 9 million rows and is growing fast. Is there anything I can do about that?