I just did an update to the list since many of us do not have edit rights to the wiki.
It looks like the threshold was around 12k USD net spend in ICs. Looks like it was calculated towards a maximum number of RAs for 2019 (per geography?).
It is not quite clear if there is an additional criteria such as 20 IC nights - but possible.
It also becomes clear that the challenge played an important role and seems to make the total spend irrelevant (in the positive and negative case).