The paper gives specific numbers for specific contexts, too. It's a helpful illustration for these concepts:

A 3x3 Rubik's cube has 2^65 possible permutations, so the configuration of a Rubik's cube is about 65 bits of information. The world record for blind solving, where the solver examines the cube, puts on a blindfold, and solves it blindfolded, had someone examining the cube for 5.5 seconds, so the 65 bits were acquired at a rate of 11.8 bits/s.

Another memory contest has people memorizing strings of binary digits for 5 minutes and trying to recall them. The world record is 1467 digits, exactly 1467 bits, and dividing by 5 minutes or 300 seconds, for a rate of 4.9 bits/s.

The paper doesn't talk about how the human brain is more optimized for some tasks over others, and I definitely believe that the human brain's capacity for visual processing, probably assisted through the preprocessing that happens subconsciously, or the direct perception of visual information, is much more efficient and capable than plain memorization. So I'm still skeptical of the blanket 10-bit rate for all types of thinking, but I can see how they got the number.