I think she's quoting pg, but pg lists the condition of that growth to be the time a startup is in the YC class

    A good growth rate during YC is 5-7% a week. If you can
    hit 10% a week you're doing exceptionally well. If you
    can only manage 1%, it's a sign you haven't yet figured 
    out what you're doing.

http://paulgraham.com/growth.html