Sounds like you need to read this:
https://en.bitcoin.it/wiki/Coin_analogyAnd this:
https://en.bitcoin.it/wiki/ChangeYou attempted to send 50 BTC, but your biggest UTXO looks to have been 49.99915808 BTC, so your wallet added in extra inputs to make up a total of over 50... Not sure why it needed to use another 12 inputs when pretty much any of the other ones with would have been plenty for 50+fee! Possibly some weird glitch in the UTXO selection algorithm that your wallet is using??
Anyway, it totalled up 88+ BTC, but you only wanted 50, so it put the remaining 38 into a change address in your wallet...