Jio Platforms is all set to make its much-awaited market debut this week, with the grey market continuing to signal decent listing gains of a little over 22% for the IPO allottees of the mega issue of the Mukesh Ambani-led Reliance Industries arm.Ahead of listing, the unlisted shares of Jio Platforms were trading at Rs 1,366 apiece in the unofficial grey market. This marks a grey market premium (GMP) of Rs 247 per share or 22.07% over the upper end of the price band of Rs 1,119 apiece.