Articles by Hindustan Times and ANI News confirm that over 1000 people gathered at the event after the lockdown had been imposed by the government.
Similarly, ANI News and India Today also reported that more than 3,400 people had attended the Tablighi Jamaat event in Delhi. After the Janata Curfew had been announced, about 1,500 people left and around 1,500 had remained back at the Markaz.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.