I had use uniswap on an old wallet unfortunately I lost those wallets so no 400 UNI 
. You cannot benefit from it because you will have to use it not in September, For august.
Recently i try to trade on uniswap in order to get also the 400 uni but i think the airdrop is already finish and i wont get any uni by trading on uniswap, but im hoping there will be another airdrop soon. . You cannot benefit from it because you will have to use it not in September, For august.