The contest has started today and it will go on for next one month.
Tom Derrick, the digital curator of the Two Centuries of Indian Print
project of British Library, has published a blog post about it on BL
BL has also tweeted:
On Tue, Mar 2, 2021, 20:07 Bodhisattwa Mandal <bodhisattwa.rgkmc(a)gmail.com>
We are happy to announce that the West Bengal Wikimedians User Group 
will run a proofread contest  from 15 March 2021 to 14 April 2021 on
Bengali Wikisource in collaboration with Two Centuries of Indian Print
project (TCIP)  of British Library.
The TCIP project officials are uploading the public domain books under
their collection on Wikimedia Commons . From the user group, we are
working on the next steps like renaming files, indexing, metadata related
work on Wikidata etc. and will be organizing the event.
The top five winners will receive T-shirts and/or books from the user
group and digital certificates from British Library.
On behalf of West Bengal Wikimedians User Group