What you see is the "change" part of the transaction.
When you make a bitcoin transaction, you cannot send a partial "coin". That means that if you have received 0.2 BTC in one transaction, you have to spend 0.2 BTC in one transaction. The way this is handled is by sending 0.001 BTC to the recepient, and 0.199 BTC back to yourself. Now you have a new "input" of 0.199 that can be used for your next transaction.
Your transaction can combine multiple "inputs" if you send a larger amount, but if an input appears it will be used entirely. The remainer is change, and is send back to yourself. Most wallets (including Armory) will create a
new bitcoin address for the change instead of reusing the old one as blockchain.info does. You can see these new addresses labeled "Change received" if you look at the wallet contents.
Experiment. Transfer another small amount to your armory wallet, send some of it back to blockchain, and look at what happens. Once you feel you understand what is going on, and are sure you can spend the money again, then you can start using larger amounts. But it is too stressful to experiment with larger amounts