Hi guys,
Noob here who read up on margin trading and thought he knew what he was doing but is now having some difficulty. I couldn't find much info on this newer Binance 10x isolated feature so hopefully someone here can shed some light for me.

Say I have $1,000 USD, want to purchase ETH/USDT (we'll say it's trading at $200/ETH), and decide to use their isolated margin platform with upto 10x margin.

I go ahead and purchase the 5ETH, and borrow 30 more, holding it in that wallet for several weeks. Now the price has gone upto $220 and I'm ready to sell, but see the site only lists my current profit on the trade as $100 for the 5 ETH, and I still have to pay back 30 ETH plus interest.

Did I screw this up majorly? Was I supposed to borrow USD or BTC initially, use those funds to buy the 30 ETH, where I could now sell them back higher and keep the leftover profit?

Or am I still able to profit on these borrowed coins that have sat here going up the last several weeks? I initially figured the borrowed coins would be tabbed at $200 as well. But now it appears that I simply borrowed 30 ETH and have to repay 30 ETH? If so, what is the point of offering these individual borrowing options of "ETH 10x" and "VET 5x." 

Thanks for reading and sorry for my mass confusion. Really appreciate the help.