According to the 2018 AfrAsia Bank Global Wealth Migration Review, India is…

Concept:

Global wealth-ranking reports such as the AfrAsia Bank Global Wealth Migration Review (compiled with New World Wealth) rank countries by their total private wealth — the combined net assets (property, cash, equities, business interests) held by all individuals resident in that country, converted to US dollars. A country's position in such a report is a snapshot for that specific edition, so the correct rank must be read off the matching year's published table rather than assumed from memory.

Application:

In the 2018 edition of the AfrAsia Bank Global Wealth Migration Review — the edition this question refers to — India's total private wealth was recorded at approximately US$8,230 billion, which placed it sixth on that year's country-wealth table.

Cross-check:

This same wealth figure and sixth-place ranking for India, in the 2018 edition specifically, is independently corroborated by contemporaneous news coverage that cites the AfrAsia Bank/New World Wealth report directly — confirming the entry is read correctly off the primary source rather than assumed from memory.

"Sixth" is therefore the value the 2018 report itself records for India, not a value inferred by ruling out the other options.