Avoiding GUI Roundoff Error wth Big Numbers?

num = "45.67e+35"
modifiednum = string.format(".0f", num)
for _,p in pairs(game.Players:GetPlayers()) do
	p.PlayerGui.ScreenGui.TextLabel.Text = modifiednum
end

Why is this giving me roundoff error? It's supposed to give me the number without any decimal points.

You can round down:

print(math.floor(4.8)) -- prints 4

Not sure how to round up tho