The Planetary Reserve levels are the amounts of resources that are to remain
on the planet. If a planet has less than the set amount ships that are set on
auto pilot mode will not pick up this resource for shipment to another planet. If
a planet has less than its reserve amount ships that are in auto pilot mode
will pick up and ship goods from other planets that have over their reserve level
and ship them to this planet.
Planet X has 5000 supplies and a reserve level of 2000. Planet Y has 40
supplies and a reserve level of 1000. A freighter in auto pilot mode will try to
pick up supplies from planet X and move them to planet Y. The freighter is free to
pick up as much as 3000 supplies, but will be picking up only 960, because
that is all planet Y currently needs to meet its reserve levels.
A planet with very high reserve levels will have resources shipped in only. A
planet with very low reserve levels will have its resources shipped out.