You can see from the picture below, the value the text field needs to show is very long.
<img src="http://dl.dropbox.com/u/34306693/floaterr.png" border="0" />
As you are only incrementing by 0.1 at a time, I would say this is not what you would expect to happen. FormatDecimal from CC would be useful here.
Ashley will be able to say whether this is expected behavior or a bug.