I believe this bug is present since 3.0.x already.
Anyway, the issue is that for admin users it is impossible to view all members, as the pager doesn't count inactive members, even though they are being displayed for admin users.

Problem is that the total members is retrieved from config in memberlist.php:1245

$total_users = $config['num_users'];

A bit further down (line 1412), when creating the query to retrieve the users of the current page, the inactive users are included in the result:

$user_types = array(USER_NORMAL, USER_FOUNDER);

		if ($auth->acl_get('a_user'))

		{

			$user_types[] = USER_INACTIVE;

		}