Shedd:

1) It is objected that it is unjust to exact personal penalty from any individuals of the human race, if a vicarious penalty equal in value to that due from the whole race has been paid to justice. The injustice alleged in this objection may mean injustice toward the individual unbeliever who is personally punished; or it may mean injustice in regard to what the Divine law is entitled to, on account of man’s sin. An examination will show that there is no injustice done in either respect. (a) When an individual unbeliever is personally punished for his own sins, he receives what he deserves; and there is no injustice in this. The fact that a vicarious atonement has been made that is sufficient to expiate his sins, does not stop justice from punishing him personally for them, unless it can be shown that he is the author of the vicarious atonement. If this were so, then indeed he might complain of the personal satisfaction that is required of him. In this case, one and the same party would make two satisfactions for one and the same sin one vicarious, and one personal. When therefore an individual unbeliever suffers for his own sin, he receives the due reward of his deeds, Luke 23:24. And since he did not make the vicarious atonement “for the sins of the whole world,” and therefore has no more right or title to it, or any of its benefits, than an inhabitant of Saturn, he cannot claim exemption from personal penalty on the ground of it. Shedd, Dogmatic Theology, 2:443.

2) The other injustice alleged in the objection, relates to the divine law and government. It is urged that when the unbeliever is personally punished, after an infinite vicarious satisfaction for human sin has been made, justice, in this case, gets more than its dues; which is as unjust as to get less. This is a mathematical objection, and must receive a mathematical answer. The alleged excess in the case is like the addition of a finite number to infinity, which is no increase. The everlasting suffering of all mankind, and still more of only a part, is a finite suffering. Neither the sufferer, nor the duration, is mathematically infinite; for the duration begins, though it does not end. But the suffering of the God-man is mathematically infinite, because his person is absolutely infinite. When, therefore, any amount of finite human suffering is added to the infinite suffering of the Godman, it is no increase of value. Justice, mathematically, gets no more penalty when the suffering of lost men is added to that of Jesus Christ, than it would without this addition. The law is more magnified and honored by the suffering of incarnate God, than it would be by the suffering of all men individually, because its demand for a strictly infinite satisfaction for a strictly infinite evil is more completely met. In this sense, “Where sin abounded, grace did much more abound,” Romans 5:20. Shedd, Dogmatic Theology, 2:444.