Sometimes that 200 is just what is on the shelf !!. There are more in the storage. It does not mean that if you buy all that 200 contracts the price will go up one point. Any purchase will create a buying pressure even a minute one but market is more fluid than your trades. After you buy all 200 contracts, because of market condition, the price might even drop 10 points ore more (just the second you are buying). As a small trader, you don't buy to push the price up (specially the futures). You buy it because you believe it is in a trend that you hope or that trend will happen in the near or your target future. The 200 order might be an iceberg order and 200 is only the tip of it. In this case, when you buy 10 contracts, you would see that 200 does not change.