BI Publisher Assistance

I need to format a time field to Gregorian format. My data is hhmmss currently and I need to get it to hh:mm:ss.

I have been trying to substring the field and concantenate where needed. this is what I have

<?xdofx:if  length(BeginningHhMmSs_ID18) = 5 then

concat ( substr(BeginningHhMmSs_ID18,1,1),':')

else concat( substr(BeginningHhMmSs_ID18,1,2),':')

end if?>

and this is what is returned

0.00083333333333333333

Can someone explain to me how this is possible and what I can do to fix it? I am working on a RTF template.