When you sell your home in the US and you are a Foreign National the US Government will want to make sure taxes are paid if they are due.
10% of your sale price is held in a fund for this review. The 10% withholding is not a tax or fee. It is just withheld until the sellers file their US taxes to claim any capital gains. If there are no capital gains, the 10% would be refunded to them. However, they may not be able to file the taxes until Jan/Feb of next year. In order to avoid that, here is what I found regarding the 10% Withholding:
Here is the IRS Link: https://www.irs.gov/individuals/international-taxpayers/firpta-withholding