The Answer:
Your FnO turnover, as the article you’ve linked indicates, is not the sell value of all the contracts you’ve sold. Its the absolute aggregate of both your gains and losses. Refer to this intra-day turnover calculation for reference.
A Suggestion:
Its considered best practice to get your books audited by a chartered accountant every year if trading/investing income is a significant part of your Total Income. There is always the off-chance that in the future your file may get scrutinized by an ITO who might not have great understanding of the markets and quiz you on multiple book treatments. Thereby causing much loss of time and energy to you. Audited books on your end will bring peace of mind.
Hopefully, this helps. Cheers,