It appears from other sources that they are referring to mass. The event horizon for a non-rotating black hole is about 3 km for each solar mass, so these bad boys would have an event horizon of more than 20 astronomical units, or about out to the orbit of Saturn if placed in the same position as our sun. < shudder>
Scratch that. Make it beyond the orbit of Uranus. (Saturn is only about 9.4 AU, Uranus about 18+) More shuddering.