How do I make this more accurate?

function tween(part,pos,tim,stop) --stuff
	local function stuff() --for the stopige
		local runs = 100 --smoooth
		local ToTake = runs*.03 --time it will take
		if ToTake>tim then
			repeat
				runs=runs-1
				ToTake = runs*.03
			until ToTake<tim --gets closer to tim
		else
			repeat
				runs=runs+1
				ToTake = runs*.03
			until ToTake>tim
		end
		local cf = part.CFrame --start cf
		for q=runs,0,-1 do
			wait()
			part.CFrame = pos:lerp(cf,q/runs)
		end
	end
	if stop then --stop! In the name of lo-o-o-ove
		stuff()
	else spawn(stuff)
	end
end

return tween

The above is a moduleScript. The purpose of it is to smoooooothly move parts. It works fine, but if I do something like this.

p1 = game.Workspace:WaitForChild("Part")
p2 = game.Workspace:WaitForChild("Part2")
tween = require(game.ReplicatedStorage.tweens)

start = tick()
tween(p1,p2.CFrame,10,true) --it has to pause here
print(tick()-start) --print 11.3

So, does anybody know how I could improve the accuracy of the time?