I hope you were not expecting the seller could pay any part of your down payment. It is not allowed by FHA, even if the seller wants to.
It is normal for closing costs to eat up anywhere from 3 to 6% extra over the purchase price. Those closing costs are above and beyond the down payment requirement.
Sellers are allowed to contribute funds toward the closing costs but not a cent to the buyers down payment.
FHA loans are more complicated than conventional loans. There is something called mortgage insurance premium (MIP) that is added to the base loan amount. This MIP charge complicates FHA loans enormously for escrow and loan officers and for buyers.
You have a base loan amount, then there is the total loan amount which is base plus MIP.
The MIP is financable - that means you can add it to the loan balance. This of course increases your loan balance and the amount of your monthly payment. Is this what your extra $4,000 is?
Or. If you put up $2,000 as the initial deposit - and you are now being asked to bring in $4,000. Well this is simple math 2 + 4 = 6.
That would sound right, - the balance of the down payment....
However, if you (for example) were buying down the rate of your loan, or had extremely high commissions for a lender, or had agreed to pay some other costs,..... then you could still need to pay some money at closing.
Make sure someone explains it to you, and hopefully before you go to the signing. As you're not familiar with it, it might make it easier to absorb if you try to do it ahead of time.
Good luck and congratulations.
Congrats on your new home!!
Without looking at your HUD 1 statement I can not give you the proper answer. I would suggest you speak with your Mortgage Officer or Attorney and have them explain this to you.