From: Houston, TX
Ok, thanks. Let me reword last question. If you have a single supply source, would 10 units get less supply than three units? This assumes everything else is equal. In other words, a hex 10 hexes away from the supply point would receive the same amount of supply regardless of the number of units the source is feeding.
As far as the game is concerned, a supply point is inexhaustible. It will supply 1 unit or 10,000 units equally.
But, as the scenario designer, you can account for this yourself if you desire some effect. If the number of units in theater suddenly expands beyond the limits of the supply net, you should drop the Force Supply Level accordingly. (But only if that truly was the case: In reality, units tend to come with their own supply network.)
Off topic: Don't forget about the Supply Radius. That's a critical parameter that so many designers overlook.