I think the HTML table uses ltmPoolMemberStatServerCurConns from mysql, but ltmPoolMemberStatServerTotConns is also polled, is ltmPoolMemberStatServerTotConns used for the RRD input? Maybe this is where the disagreement starts, in the file /opt/observium/includes/polling/loadbalancer/f5-bigip-local-mib.inc.php
It makes sense these wouldn't agree, if the connections mostly last longer than a polling period. The delta of ltmPoolMemberStatServerTotConns values would be the number of NEW connections in a polling period, and ltmPoolMemberStatServerCurConns reflects the history of several polling periods for outstanding connections. So connections mostly lasting for 10 polling periods for example would make a 10x difference in these values.
Both metrics are useful to see, so maybe can this be explained more clearly in the UI, or maybe graph both values?
Added "/sec" to graph legend