if big == true then
big = false
btnframe.Parent.Parent:TweenSize(UDim2.new(btnframe.Parent.Parent.Size.X.Scale/rate, 0, btnframe.Parent.Parent.Size.Y.Scale/rate, 0), Enum.EasingDirection.Out, Enum.EasingStyle.Sine, 0.3)
end
On this line put big = false after you execute the tweening.