Volume Slider Value in Options Menu not Changing

I've been working on this options menu and I'm trying to add sliders for volume. I've been using this video as a guide link text. At about 8:30 he starts to make changes in the script to have it so the value of the number next to the volume slider will match the value in the slider. I followed the video step by step but the value on the right of the slider won't change. My goal is to have the number next to the slider change like in the video at 10:53. How do I get this to work?