Some currencies have a minimum amount for deposits, this amount is written at the deposit page under each currency deposit address.
If you send less than the minimum by mistake, you can simply send more until the balance of the deposit address is above the minimum, you can use a block explorer to track the address balance, simply search for your Poloniex deposit address on the block explorer to check exactly how much you already have at your deposit address and how much you still need to send.
|Coin Name||Minimum Amount|
|ETC / LSK / EXP||1|
|BURST / NXT / BCY||5|
Please mind the network fee when making the transaction, 0.5 ETH after the network fee will be .49 ETH, if the minimum limit is 0.5 ETH the .49 ETH will not credit until more ETH is sent. This apply to all coins with a minimum deposit limit.
Once the deposit address is funded with enough balance the whole amount will be automatically credited to your Poloniex account.