Exactly, this number is conspicuously absent from any stories about this. Googling for this information ("hummer preorders") only finds a bunch of similar articles about being sold-out, or reserved-out, with no numbers either.
The following article credits Electrek.co with the info, but no mention of it on their website.
https://www.motor1.com/news/450123/hummer-ev-edition-1-sold-...
I wonder if there will be vocal GM short-sellers now too.