Sorry, your right, mhdpHdGbkoTXCfkZZQhJUgQrFiTytwB5gu sent, but why the remaining balance went to mknda3aU9LH4BAL2eqeegQRnShhQawoUWo instead of going back to mhdpHdGbkoTXCfkZZQhJUgQrFiTytwB5gu ?
It's the change address (
https://en.bitcoin.it/wiki/Change). Bitcoin-qt will automatically assign a change address for every transactions that have changes unless you turn off the feature