Having trouble with the tutorial "Keeping Score"

Hey, okay so we are trying to use this coding with another game. We have a different layer for scoring, and for our different buttons, and we followed the tutorial. However, when we click the button, the score goes to 100 once, and then just continues showing 100 repeated in the text box. I would link the file, but it is too large! Also, the button that decreases the score keeps giving us the NaN problem. Please help. Thanks!