Re: Parmatthajotika question

Dear
Friends,
 
In the introduction to the Parmatthajotika II (PTS 1,1, commentary on the Sutta
Nipāta) the following verse occurs:

sabbāni cāpi suttāni, pamāṇattena tādino
vacanāni ayaṃ tesaṃ nipāto ca yato, tato
aññasaṅkhānimittānaṃ, visesānam abhāvato
saṅkhaṃ Suttanipāto ti, etam eva samajjhagā ti

Rough
translation attempt: “And all the suttas (and) words, according to the amount of such (tādino, i.e. the Sutta Nipāta?), because (yato) this is a collection of
them, therefore (tato) it is called by name “Sutta Nipāta,”  because of the absence of differences occasioned
by others’ calculations (?añña-sankhā-nimittānaṃ)
, I (or "he has..."?) have understood that clearly (samajjhagā = adhigato per
It-a 2, 95).”
 
What
does saṅkhā mean here?  The
translation does not seem right.
 
and
the commentary begins by an allusion to the last line above, with samadhigatasaṅkho:
evaṃ
samadhigatasaṅkho ca yasmā esa vaggato uragavaggo, cūḷavaggo, mahāvaggo, aṭṭhakavaggo,
pārāyanavaggoti pañca vaggā honti
“And
in this way, since the calculation (saṅkho?) has been fully understood, in
the book there are five chapters: the Uraga, Cūḷa, Mahā, Atṭhaka and Pārāyana
chapters.”

I’m
wondering what the meaning of saṅkh- is here? presumably from saṅkhā (“enumeration,
calculation,” but can also mean “understanding, meaning, name,” Also, if it
does mean “calculation” why does ti have a masculine ending, as it is a fem.
noun and I don’t see a bahubbīhi here?
 
Thanks
for your help,
 
Bryan

[Non-text portions of this message have been removed]