New to Premiere Pro - Issues with Key Frames

Hi, I had a question about motion graphics. I'm trying to make a fadeaway key-frame effect, with the yellow box expanding and then the text disappearing as the box shrinks to the left. However, when I add a new keyframe it keeps altering the previous curve, leading it to somewhat expand and shrink incorrectly. I've attached the two videos (before and after), and I've attached the curves for each one. 

Any help is greatly appreciated!