The number range facet type
The number range facet type allows your users to filter your listings by using numerical values. Example: if you were to create an Airbnb like directory, you might have a field for the number of maximum guests in a house/room.
Other data source: if you're filtering 2 numbers, the option allows you to select a secondary field from where the data is coming from.
Fields to show: you can choose whether you wish to display a min and max field together, an exact numeric field or min and max field as individual fields.