User blog comment:Primussupremus/Extended busy beaver or super sigma./@comment-29915175-20170406195949/@comment-3427444-20170407072011

In Scott Aaronson's article Who Can Name the Bigger Number?, which is mentioned on the blog post, defines BB(n) as the maximum number of steps a n-state TM can take before halting, rather than the maximum number of non-zero symbols at the point of halting. The writer of this blog seems to use the same notation definition for it.