If the account had just the $19,500 to begin with and the value of the account at the time of the distribution is $13,000, to accomplish a return of an $18,500 excess contribution the administrator will calculate the loss-adjusted amount to be distributed as $18,500 * $13,000 / $19,500 = $12,333.33. All you should need to do is tell the administrator that you have a $18,500 excess contribution and they should do the rest, but make sure that they calculate the loss-adjusted amount correctly.
