Formosa Petro, a Taiwanese oil giant, lost $3 billion in in market value after a "fat finger" error mistakenly caused the company to open a 15.2 million-share closing auction, according to Bloomberg. A "fat finger" error is, literally, a keyboard typo and, in this case, a very expensive one indeed. The 15.2 million shares, a trade valued at more than $55 million, was far higher than the company's average 2.9 million share volume for full-day sessions since September, said Bloomberg. The exchange found the mistake, however, and said that brokerages will need to apply to the exchange in order to fix them. Still, the lesson is clear: alweays, always, always mak sure to double-check for tyops.