How can I make this accurate as possible?

Ok,so I want to make a Playlist with songs in it and inside that playlist there is going to be a progress bar that starts to fill up all the way until the end(almost like the youtube progress bar).I tried it but it wasn't so accurate.

bar = script.Parent
sound = Instance.new("Sound",bar)
sound.SoundId="rbxassetid://154587535"
sound:Play()
for i = 0,10,1 do
    wait(8.7)
    bar:TweenSize(UDim2.new(i/10,0,0,80),"In","Linear",1,true)--Makes the size to 0.1 to 1
end