The annual maximum amount may be awarded to you as a combination of subsidized and unsubsidized. You must pay the interest on the portion that is unsubsidized while in school, and during any grace or in-school deferment periods, unless you elect to have the interest added to the principal. This is called capitalization. Having the interest capitalized will mean larger payments when you begin repayment.
Most federal student loans have loan fees that are a percentage of the total loan amount. The loan fee is deducted proportionately from each loan disbursement you receive. This means the money you receive will be less than the amount you actually borrow. You're responsible for repaying the entire amount you borrowed and not just the amount you received.