Both numeric data types are stored as a number in a DOUBLE column in the database. To set numeric data, a number must be passed to the according setter. The two fields merely differ in their GUI input widgets and the fact that the slider has a min/max value and step size, which the numeric field does not have.
Numeric
The numeric data field can be configured with a default value. In the GUI it is represented by a spinner field.
Slider
In the GUI a slider can be used as a horizontal or vertical widget. It needs to be configured with a min and max value, the increment step and decimal precision.
