Once activated it will periodically refill all the resources (except ElectricalCharge) on a vessel. The resupply time is based on the distance from the selected celestial body. It's completely based on a 'player honor system'.
For example a ship orbiting Laythe will take ~1 Day for a resupply from the planet's surface. But will take longer from any other celestial body.
Raw stats are from the beginning of time until now. Each follower and download entry represents one hour of data. Uneventful hours are omitted.