NetSuite SuiteScript FOR loop and IF statement Confusion

I am working through a free freight script in our NetSuite environment. I have the code looking at the line item in which has a check box for "Exclude Free Freight" on each line - this is pulled from the item master. The problem is, I cannot seem to get the IF statement to run this through correctly. Ultimately, I am asking to sum up all the excluded items on the final variable. Here is my code.

try{

var totalQuantity = 0;
    var flTotalItemAmount = 0;
var flAmount = 0;
var itemCount = newSOIDbfs.getLineCount('item');
    log.debug("itemCount:", itemCount);

for (var i = 0; i < itemCount; i++) {

var stExcludeFromFreeFreight = newSOIDbfs.getSublistValue('item', 'custcol_exclude_from_free_freight', i);

if(stExcludeFromFreeFreight != 'F')
    {
    log.debug("Free 1:", stExcludeFromFreeFreight);

    flAmount = newSOIDbfs.getSublistValue('item', 'amount', i);
        log.debug("flAmount:", flAmount);
    flTotalItemAmount = forceParseFloat(flTotalItemAmount) + forceParseFloat(flAmount);
        log.debug("flTotalItemAmount:", flTotalItemAmount);

} // end if statement

} // end for loop
} // end try statement
   catch(exception){
   log.debug("GetInputDate Error Message:",exception);
}

The resulting Debug looks like this:

The end result is we have 3 lines on the sales order, 2 lines are free freight eligible and one line is free freight excluded. Final variable flTotalItemAmount should be $183.75.

Anybody see what I am missing and why the IF statement is taking lines 0 and 1 into account?

In SuiteScript 2.x, checkbox values are booleans - true if the checkbox is checked; false if it is not checked. You can see evidence of this in your Free 1 log statements.

Your comparison condition can be reduced to if (stExcludeFromFreeFreight).