Tattha anupasampannānaṃ sīlaṃ gaṇanavasena sapariyantattā pariyantapārisuddhisīlanti veditabbaṃ.
Ñ(I,132): (a) Herein, the virtue of those not fully admitted to the Order should be understood as virtue consisting in limited purification, because it is limited by the number [of training precepts, that is, 5 or 8 or 10].
‘‘Nava koṭisahassāni, asītisatakoṭiyo;
Paññāsasatasahassāni, chattiṃsā ca punāpare.
Peyyālamukhena niddiṭṭhā, sikkhā vinayasaṃvare’’ti. –
Ñ: (b) That of those fully admitted to the Order is [describable] thus:
Nine thousand millions, and a hundred
And eighty millions then as well,
And fifty plus a hundred thousand,
And thirty-six again to swell
The total restraint disciplines:
These rules the Enlightened One explains
Told under heads for filling out,
Which the Discipline restraint contains.
Sayādaw U Sīlānanda: 91,805,036,000 (Chew: 9,185,036,000)
Han: Burmese translation: 91,805,036,000. (same as Sayādaw, and same as the Pāḷi text).
Pāḷi: Nava koṭi sahassa = nine koṭi thousand = 9,000 koṭi
1 koṭi = 10 million
therefore 9,000 koṭi = 90,000 million.
It is quite a big exaggeration, I think. The total world population at that time could not be 9 billion, let alone 90 billion.
Evaṃ gaṇanavasena sapariyantampi anavasesavasena samādānabhāvañca lābhayasañātiaṅgajīvitavasena adiṭṭhapariyantabhāvañca sandhāya apariyantapārisuddhisīlanti vuttaṃ, ciragumbavāsikaambakhādakamahātissattherassa sīlamiva.
Ñ: So although limited in number,  it should yet be understood as virtue consisting in unlimited purification, since it is undertaken without reserve and has no obvious limit such as gain, fame, relatives, limbs or life. Like the virtue of the Elder Mahā-Tissa the Mango-eater who lived at Ciragumba (see §122 above).