What are, according to the sutras, the three continents resonating with Weituo Bodhisattva? Why delivering and transforming only three of them?

The three continents resonating with Weituo Bodhisattva are

Purvavideha in the east, Jambudvipa in the south, and Aparagodaniya

in the west. According to the sutras, Mount Sumeru in the center is

peripherally surrounded by four continents, which are the three

aforementioned plus Uttarakuru in the north. Weituo Bodhisattva

protects and guards, delivers and transforms all but Uttarakuru in

the north, where the living beings continue in joy and prosperity, are

unaware of the Dharma and life' s defilements, and hence are in no

need for help.