Tax calculation commodity wise for composite dealer

This discussion concerns a registered dealer who initially opted for the composition scheme with a turnover of ₹35 lacs. However, during a GST department scrutiny, their actual turnover was found to be ₹85 lacs, leading to a conversion to the regular scheme. The core question is whether the GST department's tax calculation, using commodity-wise rates instead of the composition scheme's fixed rate, is correct in this scenario.