I'm assuming someone made a mistake with decimal points.
From a programming point of view, sometimes including the decimal point in the number is a waste of space/easy to mess up, so the decimal point is left out and needs to be added in later.
For example, the Mt. Gox API tells BTC amounts in multiples of Satoshi, so 1BTC is shown as 100000000. If you forget to put the decimal back in, your calculations will be way off