This morning I was debugging an issue with an item producing low values and flapping between 0 and 1, because I set
'Type of information' -> 'Numeric (unsigned)'
'Store value' -> 'Delta (speed per second)'
and the actual item has very low, but integer values, where calculating it into speed per second was producing floats like 0,43, causing it to be stored as either a 0 or 1. The correct way to was to define this item with 'Numeric (float)'.
It might be a good idea to make note of this in the documentation, because it might not be immediately obvious that the resulting calculation from speed per second might produce floats and floats below 1.
Note: As this calculation can produce floating point numbers, you'll most likely want the Type of information to be Numeric (float), even if the raw value is an integer.