Assuming that WP-Table Reloaded uses some of the demo CSS from the DataTables distribution, there is this in the CSS (with a few other properties, although this is the important one):
.dataTables_wrapper {
min-height: 302px;
}
The idea is that it would ‘de-bounce’ paging, so when you flick pages the paging controls wouldn’t bounce around. Simply removing that min-height property would allow the table to fully collapse.
Regards,
Allan