That's just how Bitcoin works. Say you have 1 BTC on an address and you want to send 0.1 to someone, you still need to send all of the money. So wallets "split

That's just how Bitcoin works. Say you have 1 BTC on an address and you want to send 0.1 to someone, you still need to send all of the money. So wallets "split" the 1 BTC into 0.1 and 0.9 outputs, sending the 0.9 to yourself to another address you control. It's called a change address. Modern wallets do this automatically, but it can be confusing to look at it on a blockchain explorer.