From this very article: "He said officially 196 people had died from the virus in Kanpur between 16 April and 5 May, but the data from seven crematoriums showed nearly 8,000 cremations."
Here is another analysis from Gujarat: https://mobile.twitter.com/deepakpatel_91/status/13930705967...
The study that you have linked to above has primarily focused on western countries, where the process of reporting and recording of deaths is much better than in India.