How to make ores spawn with a chance depending on depth?

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1

I’m wanting to make it so ores generate with a chance as you go lower in the quarry, but I’m not sure how. I want it so that ores generate with a chance via math.clamp(Y,1,30). However, I don’t know how to make it so it clamps it properly instead of going 50 studs down it goes from one to thirty. Sorry for poor explanation.

local function selectOre(ore, Y, NoLava)
	local choice = math.random(1,100)
	if choice >80 and choice <90 then
		local orechoice = ores[math.random(1,#ores)]
		ore = orechoice
	elseif choice >=50 and choice <=52 and Y >-1000 and Y <-1000 then
		local uncommonchoice = uncommonores[math.random(1,#uncommonores)]
		ore = uncommonchoice
	elseif choice >=30 and choice <=31 and y <-2500 then
		local rarechoice = rareores[math.random(1,#rareores)]
		ore = rarechoice
		elseif choice >=0.1 and choice <=1 and Y <-4000 then
		local legendarychoice = legendaryores[math.random(1,#legendaryores)]
		ore = legendarychoice
	elseif choice >5 and choice <5.5 and Y <-5000 and NoLava == nil then
		ore = game.ReplicatedStorage.Ores.Lava --Lava
	elseif choice >70 and choice <=100  and Y >-200 then
		local solidorechoice = solids[math.random(1,#solids)]
		ore = solidorechoice
	else
		if Y >-100 then
			ore = game.ReplicatedStorage.Ores.Dirt
		elseif Y <-100 and Y >-4000 then
			ore = game.ReplicatedStorage.Ores.Stone
		elseif Y <-4000 and Y >-7000 then
			ore = game.ReplicatedStorage.Ores.Basalt
		elseif Y <-7000 then
			ore = game.ReplicatedStorage.Ores.Hellstone
		end
		return ore
	end
	return ore
end

EDIT: I’ve not put the whole script in, since I’m worried it can be copied off of.

2

Have you tried making the ores spawn frequency dependant upon the Rarity * Y?