GLOBAL_RESOURCE exospheric definitions

[KspNoobUsernameTaken]

So I was looking at the resource definitions in karbonite, and found these examples for exospheric resources:

// GLOBAL EXO
GLOBAL_RESOURCE
{
	ResourceName = LqdHydrogen
	ResourceType = 3

	Distribution
	{
		PresenceChance = 50
		MinAbundance = 1 // .00000001 - Relative atmospheric scaling applied
		MaxAbundance = 100 // .00000005 - Relative atmospheric scaling applied
		MinAltitude = 500
		MaxAltitude = 200000000000
		MinRange = .01
		MaxRange = .5
		Variance = 20
	}
}

// SUN EXO
PLANETARY_RESOURCE
{
	ResourceName = LqdHydrogen
	ResourceType = 3
	PlanetName = Sun

	Distribution
	{
		PresenceChance = 100
		MinAbundance = 10 // .00000001 - Relative atmospheric scaling applied
		MaxAbundance = 20 // .00000005 - Relative atmospheric scaling applied
		MinAltitude = 0.1
		MaxAltitude = 500
		MinRange = 500
		MaxRange = 500
		Variance = 0
	}
}

Could someone explain how min altitude and max altitude work?  Also, what does he mean by //(stuff here) - Relative atmospheric scaling applied? Lastly, what does minRange/maxRange and the Variance do?