Largest equity bourse NSE on Friday announced final contours of its much-delayed initial public offering (IPO), with existing shareholders cutting the quantum of their holdings to be sold and a final price band, which is lower than what was broadly expected.The entire issuance comprises an offer for sale (OFS) from the existing shareholders, and with a price band of Rs 1,700-1,785 per share, the exchange will mop up between Rs 21,494 crore and Rs 22,569 crore from the issue, which opens for subscriptions on September 17.Existing shareholders have offered only 12.64 crore shares for sale as against the initial indication of 14.9 crore shares to be sold, while the price per scrip has declined from a high of around Rs 2,400 seen in the grey market.The bourse's Chief Executive and Managing Director, Ashishkumar Chauhan, told reporters that long-time investors had indicated a higher quantum of shares to be sold at the time of filing papers earlier this year, but the same got reduced.They may have done so to keep their skin in the game and get some upside in the future, he said.The price band was decided by a team of 20 merchant banking entities advising NSE, he said."After deliberations and roadshows across the world, our merchant bankers have advised us that this is the price," he said.It can be noted that the festive-time IPO -- next Monday's Ganesh Chaturthi kicks off the festive season -- comes at a time when the markets are witnessing high volatilities. There have been few issuances lately, but they have been of smaller sizes.NSE's IPO, which was initially believed to raise over Rs 30,000 crore, will become the second biggest to date in India after South Korean carmaker Hyundai Motors' Rs 27,870-crore issue and a tad higher than the Rs 21,000 crore raised by insurance behemoth LIC.Jio Platforms' is also readying for a Rs 37,700-crore issue to be launched during the festival period itself.On the critical issue of whether NSE's shares will be listed on its own platform, Chauhan said they have not written to capital markets regulator Sebi seeking any go-ahead on the same.On NSE's over-reliance on the options segment for its revenues and challenges, given capital markets regulator Sebi's actions to reduce activity in order to protect investors, NSE officials explained that the share of revenue from this stream has been coming down over time.Overall, from a regulatory challenges perspective, Chauhan said the exchange has seen a lot of actions in its over three decades of existence but added that the same has been aimed at helping consumers and every such action leads to an expansion in the investor base, which ultimately helps the exchange.Subscriptions for the general public will open on September 17 and close on September 21, as per official documents, which also said the listing will happen on September 24.The issue will have a reservation of 50 per cent for qualified institutional buyers (QIBs), 15 per cent for non-institutional investors (NIIs) and 35 per cent for retail investors.As per the red herring prospectus (RHP), existing shareholders have also pared down their stake sale.State Bank of India (SBI) has reduced its proposed OFS to around 1.60 crore shares from 2.47 crore shares, while MS Strategic (Mauritius) Ltd has cut its offer to 1.1 crore shares from 1.6 crore shares.Bank of Baroda, Stock Holding Corporation of India Ltd and General Insurance Corporation of India have also reduced their proposed share sale, while SBI Capital Markets Ltd is a new selling shareholder in the RHP.Since the issue is entirely an OFS, proceeds from the share sale will accrue to the selling shareholders and not to NSE.The public issue marks a major milestone for NSE, after markets regulator Sebi last week gave clearance to the exchange to proceed with the offering.Its listing plans remained stalled for nearly a decade amid regulatory hurdles, including the co-location controversy.