I just realized the example on the same page (page 6) hints at the answer: "For example, [1H2J2j;YNG42A] gives [1 2 2 j 2j; inf NaN -j 42 5]." Looks like the

I just realized the example on the same page (page 6) hints at the answer: "For example, [1H2J2j;YNG42A] gives [1 2 2 j 2j; inf NaN -j 42 5]." Looks like the codes are to avoid printing spaces by alternating with digits. Ugh, but ok. Code golf. Sigh.