Phantom score on results slide

I have prepared a 24 question quiz where there are no right or wrong answers, but I do want a score.  

• 12 questions are worth either 0 or +1, the other 12 are worth 0 or -1.  
• I have defaulted the "right" answer to be the one worth 0 on every question.
• All questions are worth 0 points.
• I am counting the number of slides answered so that can be reflected on the Results slide.
• I have put in a "Skip question" button so that people can skip to the next slide, potentially skipping all questions.  
• Every slide is set up so that Button 1 (Skip to next question) comes first. The Player Trigger (Add 1.00 to SlidesAnswered when the user clicks the submit button and Submit interaction Multiple Choice when user clicks the submit button) comes second.

When I tested skipping all of the questions, the results slide came back with a score of -1 on 0 questions answered.

Is there anything else I need to check?

Help! I'm on a tight deadline with this.

Cheers

KerryJ

kerry.johnson@unisa.edu.au