GIFT Nifty — the contract formerly listed in Singapore as SGX Nifty — is a Nifty 50 futures contract traded on NSE International Exchange at GIFT City. It runs across two sessions that together cover far more of the clock than the NSE cash market, so it keeps pricing Indian equity risk while the domestic market is shut.
That is why it is read as a pre-market indicator: overnight moves in US equities, crude and the dollar show up here before the NSE opens. It is an indication of sentiment, not a prediction of a specific Nifty level, and it is best read with the option-chain positioning linked above.