it depends if you are HKG based and a bonefide overseas resident or living in the USA. Claim what you get subtracted from what the you are entitled to from the US state dept site you mentioned. Mine used to work out to about 4000 US$ advantage per year.
next time you fly just write down the allowance money you received on your roster. save those twelve rosters and record keeping is a breeze. ie days away from home etc. Vol 1 also list what allowances you get.
That tax advice is pro bono, you want more info you PM me and we can talk