According to this comment on Reddit:
You actually need a simple majority YES vote from ALL eligible neurons. As at today, if Dfinity Foundation & ICA don’t vote, you can’t get that, since most neurons follow them.
If this is the case, I think it would make sense to display the breakdown of all eligible votes instead of just a breakdown of votes cast.
I imagine this would make the chart look something like
Didn’t vote | Yes | No instead of just
Yes | No