Journal Entry Line Numbers Mis-Match

I have the following code:

         var tranRecord = nlapiLoadRecord('journalentry',tranIntId);            tranRecord.setLineItemValue('item','class',tranLine,projClass);          tranRecord.setLineItemValue('item','department',tranLine,projDiv);          tranRecord.setLineItemValue('item','location',tranLine,projLoc);          nlapiSubmitRecord(tranRecord); 

This loads a journal entry with the given Internal ID and tries to change the line

tranLine

class/department/location depending on what is on the corresponding project.

What this does however, is change the previous line's classifications.  For instance, I have a given journal entry whose line 266 I want to change but this code is changing line 265.

I tried changing it to

tranLine + 1

but that doesn't seem to change anything.