The 'Top Users' option defines the number of entries for the table with the users, which most often visited your site, as long as you have to login with a username and a password to get access to parts of your homepage.
The table may be disabled by using zero. The 'Show All' checkbox allows the display of all users. If enabled, a separate HTML page will be created, and a link will be added to the bottom of the 'Top Users' table. There are a couple of conditions for this to occur. First, there must be more items than will fit in the 'Top Users' table. Second, the listing will only show those items that are normally visible, which means it will not show any hidden items. Grouped entries will be listed first, followed by individual items. Please be aware that these pages can be quite large in size, and separate pages are generated for each month, which can consume quite a lot of disk space depending on the traffic to your site.