Правило 15
A link to the Book of Acts of the Apostles about the 7 deacons in one city, even a large one.
According to the rule, there should be 7 deacons, even if the city is very large. And you will be convinced of this from the book of Acts.
Greek original
Διάκονοι ἑπτὰ ὀφείλουσιν εἶναι κατὰ τὸν κανόνα, κἂν πάνυ μεγάλη ᾖ ἡ πόλις. Πεισθείσῃ δὲ ἀπὸ τῆς βίβλου τῶν Πράξεων.
Parallel canons
IВс.18Трул.716Лаод.20