After checking my bitcoin account after two years, 0.00010757 of a bitcoin remains even though I explicitly remember having half a bitcoin left. My first thought someone somehow stole it. But after looking through my transaction history, it seems that there were additional transactions made alongside the transactions that were made before. Below is a chart of my last three transactions made to CoinBase:

The three transactions highlighted in green were the ones that were supposed to happen but I noticed that these other mysterious transactions made alongside them also had the same IDs as the intentional transactions. The three that aren't highlighted add up to the amount that I remembered that I had two years ago, appx. 0.50055605 bitcoin. I'm not sure what these random transactions are and I'm not sure why after two years, my .5 bitcoin just vanished. I thought that the matching IDs would give me some sort of clue and it seems like these random transactions are going to a different address. Were they supposed to be sent back to my own wallet or something?

Does anyone have any ideas?

Here are the three IDs respectively: f034f9408736868ed5d070fb8fe6b5674881573815be16b791782fcdcec5d6e6
ebe2b9acce094d175577efedf8d5a1edc83ccbf5291e155a12af1c2dc5e6dd10
9cdd52384c465acd38141e6ead748cb85f74e8afef8781989e5c3592cb6bc493

I am also currently using the Bitcoin-Qt client.

Edit: After reading about it it seems like bitcoin has this change system but I’m still wondering how to get the change back and in a usable state.