Since it sounds like you are just starting out in bonds, let me first tell you a little about how bonds work before moving on to answering your actual question.
Whereas stocks represent a portion of ownership of a company, a bond (somewhat simplified) represents a portion of a company or state loan. Effectively, when you buy the bond, you are extending a loan to the entity that issued the bond.
Like stocks, bonds are traded in the public market. Like stocks, bonds can rise and fall in price as investors change their mind about whoever issued the bond. Like stocks, bonds fall in price when they are less favored by the investor collective, and increase in price when they are more favored.
Unlike stocks, how much a bond pays is fixed when the bond is issued. This is known as the "coupon" of the bond, and is often expressed as a percentage of the nominal value of the bond.
The bond also has an end date, known as its maturity or maturation date. At that date, whoever issued the bond will pay, to the current holder, the nominal value of the bond, and the bond ceases to exist. (They are paying off the loan that is represented by the bond, so the bond no longer has any meaningful reason to exist. Were it not to cease to exist, its value would be set to zero, as the money has been paid.)
A third important piece of information for a bond, alluded to above, is the nominal value of the bond. The nominal value of a bond is the amount that will be paid when the bond matures. This, too, is fixed when the bond is issued.
Now, if a bond is disfavored by the investor collective, it will be trading at below par. Another way to say the same thing is that its price is depressed, or lower than the nominal value of the bond. (The opposite is above par.) Slight variation around the nominal value is nothing to be alarmed about, but a bond trading at a price significantly different from its nominal value is a potential red flag.
One reason for a bond trading significantly below par is that the entity that stands behind the bond (in this case, Fannie Mae), is doing poorly financially. In such a situation, there is the risk of a credit event in the bond. "Credit events" are, for example, bankruptcy, debt restructuring, debt forgiveness, and so on. What this means is that if there is a credit event involving the bond, you may not get its full nominal value back at the expected maturity date, either because the nominal value is changed (sometimes down to zero), sometimes because the maturity date is changed (often to a later date), sometimes both.
In this case, the bond you purchased has a 0% coupon rate. In other words, it pays no regular interest. Any return on investment must therefore come only from the difference between purchase value and final value, and considering the time to maturity. Investors like to get a return on their investments, so it is expected to see the current value of the bond to be lower than the nominal value.
You bought the bond for $10,677, while as JoeTaxpayer pointed out, the nominal value is $15,000 to be paid in April 2027. 3.3% per year for 10.5 years corresponds to about 40.6% over those years, and just so it happens, 1.406 * $10,677 = $15,014, working out almost exactly to the difference between its current value and its nominal value. (I very much suspect that a more accurate calculation would yield a result even closer to the nominal value of $15,000.) As you can thus see, the "3.3% interest" is really a 3.3% annual return. Calling it "interest" is likely a simplification to make it more understandable.
The above calculation assumes that you keep the bond to maturity, and that no credit event occurs which involves the bond you purchased. If either of those conditions do not fully hold, then the outcome (in this case) depends solely on the difference between the price you paid for the bond and the price you sell it for, as well as any applicable tax effects.
As Eric Lippert has already pointed out in the comments to JoeTaxpayer's answer, Fannie Mae bonds are corporate bonds not backed by "the full faith and credit of the U.S. government".
Also, even government bonds come with a certain amount of risk. For a recent example, consider the 2011 Greece government debt restructuring where
Private bondholders were required to accept extended maturities, lower interest rates and a 53.5% reduction in the bonds' face value.
Greece, of course, is just one example. There are several more where large countries have needed various forms of debt restructuring in the last few decades alone.
So don't assume that even a bond that is backed by your government is a "safe" investment. History shows that it will be, until it isn't any longer.
Bottom line: Diversification remains your friend.