The plan withheld the mandatory 20% of the distribution for taxes. If this is taxed at a marginal income tax rate of 22% and you add to that the 10% early-distribution penalty, the 20% withheld will be 12% short of covering the increase in your tax liability caused by the distribution.
I'm guessing that your gross distribution was $31,250 for the plan to be able to send $25,000 to you. Given the assumptions, your increase in tax liability from the distribution is $10,000, only $6,250 of which is covered by the withholding on the distribution. After you pay the balance due, your $31,250 distribution will have netted you $21,250 (without considering any state taxes).
