Why does my experience value go into the negatives?

The >= (greater than or equal to) doesn't work and sometimes miscalculates the currentXP values into the negatives.

Is there any other efficient way to calculate this stuff?

if newvalue >= maxXP.Value then

local StarterPlayer = game:GetService("StarterPlayer")

local currentXP = StarterPlayer:WaitForChild("plrInfo").currentXP
local currentLevel = StarterPlayer:WaitForChild("plrInfo").currentLevel
local maxXP = StarterPlayer:WaitForChild("plrInfo").maxXP

currentXP.Changed:Connect(function(newvalue) 
 if newvalue >= maxXP.Value then
   currentLevel.Value = currentLevel.Value +1
   currentXP.Value = (currentXP.Value - maxXP.Value)
   maxXP.Value = maxXP.Value *1.5
  end
end)

I've tested it and sometimes currentXP is more than maxXP resulting in the exp bar not working anymore. (very rare though)

(goes into negatives): https://imgur.com/a/hhTVk14

you can test it here: https://www.roblox.com/games/4515014353/boss-scenario