If you have a Nxt (NXT) balance on Bittrex during the December 28, 2017 snapshot, you will be additionally credited the equivalent amount of Ignis airdrop tokens on a 1:0.5 basis. i.e. 1 NXT on Bittrex held during the on-exchange snapshot will get you 0.5 IGNIS airdrop tokens. NXT held on orders will also be credited. Only the NXT held on your account is eligible for IGNIS airdrop tokens.