The article being discussed (with reconstructed glyph drawings and description):

https://www.cambridge.org/core/journals/antiquity/article/id...

(PDF button not working for me, but looks like entire contents are here in HTML).

Oooh Cool. Math Bragging by "White Chested Fox" (Sak Tahn Waax), ca 800AD:

   The formula shows how one 2,920-day cycle could be divided up into the calendar units used by the Maya people. This 2,920-day cycle was important because it tied together key astronomical cycles, corresponding to both five Venus cycles (584 days each) and eight solar years (365 days each). However, the Text 19 calculations also relate the 2,920 days to Uinal (months with 20 days), Tzolkin (the 260-day sacred calendar), Tun (a year with 360 days) and Mars years of 780 days.

I wonder how intelligible classical Maya is with modern Maya languages/points on the Maya continuum. For instance, does the classical word for fox share any resemblance to any Maya word for it today?

I can imagine it going either way really but would probably guess there was vastly more drift in the case of Maya. I would naively guess that the printing press would have a dampening effect on language drift, and that the kind of repression of both the language and culture under colonialism would encourage it.

It's a shame how much was lost from some of these civilizations after colonialism. So much cool stuff gone forever.

What's the formula tho?

I still can't reconcile how they didn't use the wheel for transportation. The explanations of lack of draft animals and unsuitable terrain aren't great. Not even a wheelbarrow?