I built Frogger! (but adjusting number variable with object intersect is doing weird things)

I think my trigger is set up correctly (see the highlighted trigger in my screenshot), but I am getting 1 subtracted on the first intersection and then 2 subtracted each time after wards. 

Any ideas?

 

here's the course/game:

https://360.articulate.com/review/content/ffa0c457-5a33-42ab-90f0-219f4392ac15/review

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