Custom graph interval

Hi, I have a custom script that is working fine and graphing with no problems when I have the test launch interval set to 5m but if I change this to 10 or 15m then the graph stops updating, attached below is my graphs.cfg entry. Can someone assist me in the correct setting I need to look at for changing this correctly to update at 10 or 15 minute intervals ?

Thanks.

[sfap]
                TITLE fap utilisation
                YAXIS %
                DEF:hsfapgdef=sfap.rrd:hsfapg:AVERAGE
                DEF:msfapgdef=sfap.rrd:msfapg:AVERAGE
                LINE2:hsfapgdef#00CCCC:hourly fap
                LINE2:msfapgdef#FF0000:monthly fap
                COMMENT:\n
                GPRINT:hsfapgdef:LAST:hourly fap \: %3.1lf (cur)
                GPRINT:hsfapgdef:MAX: \: %3.1lf (max)
                GPRINT:hsfapgdef:MIN: \: %3.1lf (min)
                GPRINT:hsfapgdef:AVERAGE: \: %3.1lf (avg)\n
                GPRINT:msfapgdef:LAST:monthly fap  \: %3.1lf (cur)
                GPRINT:msfapgdef:MAX: \: %3.1lf (max)
                GPRINT:msfapgdef:MIN: \: %3.1lf (min)
                GPRINT:msfapgdef:AVERAGE: \: %3.1lf (avg)\n