The actual numbers in India are alleged to be an order of magnitude higher than the official numbers. There have been articles like [1] trying to estimate the actual numbers. The OP is likewise citing an article that's saying actual numbers are six times higher. I do not have access to the cited article to say more.

[1] https://www.nytimes.com/interactive/2021/05/25/world/asia/in...

The official Indian death numbers are a vast undercount by most accounts.

I believe he's referring to excess deaths.

Multiple sites seem to back you up. Example: https://covid19.who.int/region/searo/country/in