BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@booklet{EasyChair:6132,
author = {Shilpa Kulkarni and Sudhindra Apsingekar},
title = {A Study of Impact of GST on Indian Economy with Reference to Pune Region},
howpublished = {EasyChair Preprint 6132},
year = {EasyChair, 2021}}