LunchBox Math.RemapRange - "NaN" error


I’ve successfully created a script to read an image and create circles based on the brightness of the image.
I’ve used LunchBox’s “Math.RemapRange” to determine minimum and maximum circle radiuses.
The original image that I used to create the script works fine.
When I try to change the image, some of the numbers in my list get a “NaN” error.
Any thoughts?