The fifth continent, 2,56,00,000 yojana wide, named for the ocean of milk beyond it.
Wider than everything inside it put together - a property every ring from here outward has, because doubling makes each ring exceed the sum of all its predecessors.
That is the arithmetic that eventually makes Nandīśvara larger than the entire radius of the world it encircles.
The middle world, ring by ring - Kṣīravara highlighted