Interpolation between numbers - Libgdx

I’m trying to implement a simple “counting numbers” animation in my game. I want that whenever the score is changed, the numbers will start to count up/down until they have reached the desired number.

I tried to implement this by doing this:

points = new Label(""+ScoreManager.getPlayerScore(), skin, "default-nice") {
			private float target, rendered;
			public void act(float delta) {
				super.act(delta);
				target = ScoreManager.getPlayerScore();
                rendered = rendered < target ? Interpolation.linear.apply(rendered, target, 0.05f) : Interpolation.linear.apply(target, rendered, 0.05f);
                setText("" + MathUtils.ceil(target));
			}
		};

But it has no affect. The numbers are still changed suddently.

P.S I have one more question, not related to this topic - How can I define a fixed position to a table? I set a position for a table in my game but it can changed according to its children’s width and height.