Never saw or bothered to see it. But have used 5 times in 2 months and was never charged for using it. Its unlimited and can be used without any issue.
Actually if you check diners club black credit card (Not Metal one) page on HDFC bank site. There is two contradictory statement. Card Benefit says unlimited lounge access but FAQ says only two lounge access in a quarter. So asked to confirm which one is right and why there is two difference statement on same page. Attaching both screenshot and link https://www.hdfc.bank.in/credit-cards/diners-club-black-credit-card
Actually if you check diners club black credit card (Not Metal one) page on HDFC bank site. There is two contradictory statement. Card Benefit says unlimited lounge access but FAQ says only two lounge access in a quarter. So asked to confirm which one is right and why there is two difference statement on same page. Attaching both screenshot and link https://www.hdfc.bank.in/credit-cards/diners-club-black-credit-card