There's also remembering your strategy index tables. True, that's not a lot of numbers - some might use as few as 18 indices - but still: You're keeping in mind at the same time (a) the count, (b) a set of basic strategy rules appropriate for your specific game (c) a table of strategy variance index numbers appropriate for your specific game, (d) a deck depth estimate. And probably a few other relevant numbers.

(here's an example of the "Illustrious 18" set of strategy index numbers for one counting system: http://bjmath.com/bjmath/tcindex/i18index.htm )