blockchain – Balance in bitcoin-qt suddenly significantly diminished after a small transaction?

I had my wallet stored on a storage provider for a while, and recently got a new computer and installed bitcoin-qt and imported my wallet.

It said I had about 2 BTC and showed INGOING transactions from 2013, which I had not touched since.

I recently then transferred 0.33 BTC to another recipient, and then immediately the bitcoin balance dropped to 0.07 BTC.

I have no recollection if I have used my wallet on other computers in the time between 2013 and now, but I thought the blockchain had a perfect copy of all transactions from my wallet.

Any idea what could have happend? Can I have spend bitcoin on my wallet on another computer in say, 2015, that never got relayed to my wallet stored on cloud storage? Are the transactions stored in the wallet.dat and not on the blockchain only?

Sorry, I am confused.