I think it adds to 8%. This page [1] makes it clearer. They charge 5% and their “payment processor also charges a processing fee” which in the US is 3%.

The tip seems to be something entirely separate, which is _additional_ money, on top of your donation, that only goes to IGG, based on another [2] article.

You probably have more experience here though. Your work is great and I always appreciate your posts.

1. https://support.indiegogo.com/hc/en-us/articles/204456408-Fe...

2. https://computerengineeringforbabies.com/blogs/news/why-i-ha...