The biggest number

I have given you all an index card. You have one minute to write down the biggest number that you can (barring infinity) using any mathematical function that you know (addition, subtraction, exponentation, ackermann, Knuth's up arrow, etc). Go.

Oh, and "BB(4)" is an abbreviation for "Σ(4, 2)". Didn't see that in the wiki article. That's paired with the max shifts function, which is even bigger by definition than the busy beaver function. S(4, 2) is 107, for example.

The BB() format is more compact, though, so you'd be able to write a bigger number more quickly/in less space.

For example, with 10 characters, BB(999999) would most likely be bigger than S(9999,999) and you'd really be shooting in the dark as to the best way to optimize the matrix. So just do BB() with as many 9's as you can put in there.