I just started using blockchain.info as opposed to bitcoin-qt, and noticed right away that blockchain says my wallet has fewer bitcoins than the windows client. I started looking at the accounting of both, and noticed immediately that blockchain has incorrectly added figures starting from some of my oldest transactions. Namely here is the accounting that blockchain.info shows:

http://i.imgur.com/EzeA0rH.png

Not sure how it figures .67 minus .55 leaves a balance of zero.

Am I missing something here?