Majjhima Nikaya 3:5
SUJATOAppekacce therā bhikkhū dasapi bhikkhū ovadanti anusāsanti, appekacce therā bhikkhū vīsampi bhikkhū ovadanti anusāsanti, appekacce therā bhikkhū tiṁsampi bhikkhū ovadanti anusāsanti, appekacce therā bhikkhū cattārīsampi bhikkhū ovadanti anusāsanti.
Some senior mendicants instructed ten mendicants, while some instructed twenty, thirty, or forty.