TracingOptions and maxColors in js

Hi! I have some troubles with a script that traces a png image, and here it's my problem:

TracingOptions object has maxColors attribute, but it does nothing when I change it. At the same time, there is an undocumented attribute tracingColors that affects the result, but has a limitation at 30 maximum colors.

I want to trace my png image and have 80 colors in result svg. I use Illustrator CC 2017. Thank you!