Every user in Joomla belongs to a specifc group; this is specified in the table jos_users. The available groups are defined in the table jos_core_acl_aro_groups:

A default Joomla 1.5 installation always contains the groups (extract from the table):
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| id | parent_id | name | lft | rgt | value |
| 24 | 23 | Administrator | 15 | 18 | Administrator |
| 25 | 24 | Super Administrator | 16 | 17 | Super Administrator |
[/code:1]

So the u.gid >=24 is referring to all users which belong to the group with an ID of 24 or higher, which in standard cases would be the Administrators and the Super Administrators.

Stephan