It's one page on a web site. How much detail did you expect? They do refer to their party platform. Did you read that to look for details?

They say:

Economists have calculated that we can afford a universal basic income of $800 or more by cutting government, starting with corporate welfare and other programs that become superfluous.

Certainly a footnote would have been useful here. Maybe there is one in their party platform. But you can eyeball government spending and do some basic math yourself. $800 isn't crazy talk, if you're actually replacing other health and welfare programs.

I liked the basic principles they expressed - reduce government subsidies and tax carve outs. It surprised me to see the Greens come out in favor of that. I didn't have high expectations in the first place.