Kanji ROM ports usage/behaviour (according to portar.doc)

Hi all...

I'm doing some experiments with kanji rom (I have a perfectly working KANJI.ROM enabled GR8NET) and I'd like to know if I understand correctly the info appearing in portar.doc https://problemkaputt.de/portar.htm

If you need 16 bit to ask for a certain hex jis code inside Kanji.ROM, what do the "6 lower bit + 6 upper bit" mean in the portar D8/D9 port explanation? These 2 packed bit groups would produce a 12 bit number... and JIS codes might probably need a number bigger than 2^12...

Where's my incorrect assumption here? (to get JIS codes beyond 2**12 ?)

(We'll focus just in Kanji level 1 support, but Kanji level 2 should raise the very same exact doubt with ports DA/DB).

Greetings