How do i make it so when the player levels up, their amount of exp resets?

P1. So i am trying to make a leaderboard leveling system but when i add like 100 exp for it the level up the 100 exp stays, i want to the exp to reset or if they let say gain 10 more than the exp required to level up their exp would be 10 and their level would be the next level

player = game.Players.LocalPlayer 

game.Players.PlayerAdded:connect(function(plr)
	local ldrstats = Instance.new('Folder',plr)
	ldrstats.Name = 'leaderstats'


local lvl = Instance.new('IntValue',ldrstats)
	lvl.Name = 'Level'
	lvl.Value = 0


local xp = Instance.new('IntValue',ldrstats)
	xp.Name = 'Exp'
	xp.Value = 0
local function update()
 lvl.Value = math.floor(xp.Value/100)
end
xp.Changed:connect(update)

if player.leaderstats.Level.Value + 1 then
player.leaderstats. Exp.Value = 0
end
end)

P2. , How do i make it so that you require certain amounts of exp so level up so like at level 1 you need 100 to get to level 2 and u need 200 to get to level 3 (you wont have to answer p2)

I think this is what you were kind of looking for...

Just copy and paste in after the third one and change the 1, 200, and 300 to fit your needs

if lvl.Value == 1 then
	if xp.Value > 200 then
		lvl.Value = lvl.Value + 1
		xp.Value = xp.Value - 300
	end
end

In A Script

game.Players.PlayerAdded:connect(function(Plr)-- Player Joined
	Plr.CharacterAdded:connect(function(Char) -- Players' Character Added
		
		-- Setting Variables
		local ldrstats = Instance.new("Configuration",Plr)
		ldrstats.Name = "Leaderstats"
		
		local lvl = Instance.new("IntValue", ldrstats)
		lvl.Name = "Level"
		lvl.Value = 0
		
		local xp = Instance.new("IntValue", ldrstats)
		xp.Name = "Exp"
		
		xp.Changed:connect(function() -- Exp Value Changed
			-- Player is Level 0
			if lvl.Value == 0 then
				if xp.Value > 100 then
					lvl.Value = lvl.Value + 1
					xp.Value = xp.Value - 100
				end
			end
			-- Player is Level 1
			if lvl.Value == 1 then
				if xp.Value > 200 then
					lvl.Value = lvl.Value + 1
					xp.Value = xp.Value - 300
				end
			end
			-- Player is Level 2
			if lvl.Value == 2 then
				if xp.Value > 300 then
					lvl.Value = lvl.Value + 1
					xp.Value = xp.Value - 300
				end
			end
			
		end)
	end)
end)

And this is just a random Exp Giver

In A Script

script.Parent.Touched:connect(function(Hit)
	local PlrN = Hit.Parent.Name
	local Plr = game.Players:FindFirstChild(PlrN)
	if Plr then
		local ldrs = Plr:FindFirstChild("Leaderstats")
		if ldrs then
			local exp = ldrs:FindFirstChild("Exp")
			if exp then
				exp.Value = exp.Value + 100
			end
		end
	end
end)