User blog comment:Moooosey/Simple psi-- a fairly simple ocf/@comment-43798125-20191105221608/@comment-35470197-20191107004453

(Since I have never compared two OCFs, my guess in this comment might be wrong.)

Yes, pretty good. But PTO(KPM) is much bigger than almost all well-defined countable ordinals appearing in googology, including the current limit of your function. You do not have to mind it now so seriously.

I guess that it corresponds to level 14 in my googological ruler and to Wn scale in Letter Notation, while PTO(KPM) corresponds to level 20 in my googological ruler and to X4 scale in Letter Notation (if it extends to that realm).

I note that Bachmann-Howard ordinal corresponds to level 13 in my googological ruler, and the limit is greater than it.