In the index.php file somewhere between line 80 and 90 there is this line.
<p><?php echo $Tr_ind_station.' '.$stationtype.', '.$Tr_ind_update.' '.$interval.' '.$Tr_minutes.'<br />'.$Tr_ind_mday.' '.$rollovertime; ?>.
Change it to this:
<p><?php echo $Tr_ind_station.' '.$stationtype.', '.$Tr_ind_update.' '.$interval.' '.$Tr_minutes.'<br />'.$Tr_ind_mday.' '.$rollovertime; ?>. <br /><b>Please ensure the time/date stamp is current</b>
This will put the additional text in bold on the next line. If you want it on the same line remove <br /> so it reads
<p><?php echo $Tr_ind_station.' '.$stationtype.', '.$Tr_ind_update.' '.$interval.' '.$Tr_minutes.'<br />'.$Tr_ind_mday.' '.$rollovertime; ?>.<b>Please ensure the time/date stamp is current</b>
This is actually outside of php and is standard html.
Andy