How can this be? How can you have more futures contracts for gold than actual gold? Because you don't have to deliver a bar of gold when the contract matures. Many futures contracts settle on a "cash" basis – instead of physical delivery for the sale, the buyer receives the difference between the futures price (= the agreed-upon price) and the spot (= market) price.
There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.