That was your "change address" and it belongs to your Electrum wallet.
Notice that there's no deducted balance in your Electrum aside from the sent amount and the tx fee.
Don't worry, you can spend it too, electrum will use its output when needed.

You can disable it in the setting by selecting preference and unchecking "use change address" checkbox.
In your next transactions, the excess bitcoins will just re-sent back to the same address not to the change address. (if you're not a security freak, this won't be an issue)

Note: If you want to understand why is there a "change" or excess amount, learn how bitcoin blockchain and blocks work.