We use Nifty Wallet - you can use MetaMask with the POA RPC or another web3 wallet to withdraw any amount as long as your balance is above 100 POA. Otherwise you must withdraw the entire amount.
To withdraw the entire amount, click withdraw then click the numeric amount of POA next to Your deposit. This will fill the form with your full deposit amount. At times there may be decimals which are not in view and can impact withdrawal logic.