Okay that makes sense, but I'm only trying to send like 0.0005 BTC (plus fee). Is it normal that the change would be that much?
Yes. Think of it like cash. If you have a $20 bill and I sell you something for $5, I'm going to give you $15 in change. Bitcoin is similar. If you have 1.0 BTC and I sell you something for 0.3 BTC, how are you going to get your 0.7 BTC back? It has to go somewhere. You could send me 25,000 BTC, and I'd have to send you back 24,999.7 BTC in change. (Well, if you wanted to give me any of that change because you're such a generous person, I wouldn't complain!)