My signup admin page does not show all signup-enabled nodes. It looks as though it is showing a certain number of nodes and no more. For instance the default sort on this page is alpha ascending by title so in my case it's not showing anything with titles beginning with x, y or z. If I flip the sort to be alpha descending by title then I get the missing titles from the end of the alphabet and the a, b and c titles are left off.

If this was hard coded somehow, what file would it be in?