No such thing as FIW; should read FITW. That means federal income tax withholding. Has he deployed? And how much was the value for FIW????http://www.dfas.mil/retiredmil...nage/taxes/fitw.html
If it is the first column, then it is an entitlement not a deduction. That is added to his total unless there is a -minus sign next to the amount.
And that is ridiculous that finance will not have a clue. That is their damn job. Did you do a pay inquiry or just verbally asked? Was the finance rep a junior enlisted or NCO? If it was a junior Soldier, I would have asked to speak to a supervisor.