Just imagine someone taking out a cup of sand they safekept from your store. They wanted it delivered to their house which is 20 miles away. Obviously, the gas prices aren't cheap, so are you going to do this service for them anyway? There are operating costs to every service, and if you think 50 cents is much more valuable to get compared to the fee that you are about to incur, then you may have a few screws loose in your head.
Clearly the most reasonable thing for him to do is to leave the 50 cents, because any attempt to withdraw it will make no economic sense. Ofcourse he must've understood that not withdrawing will attract him to pay the $20 fee, since he did not, then it's best that he leaves the balance as it is, hopefully when he funds it with a substantial amount, then he can think of withdrawal.