"But when he is found he must repay sevenfold; he must give all the substance of his house"
Solomon is reminding the Jewish listener of the laws of restitution in the Old Testament. If a thief were to steal something from you, then depending upon the condition that you found out who did it and whether they still had it with them, the thief would have to repay you twice, four times, or seven times the value of the item that they stole as well as what they stole.
In this system of justice there is real opportunity for forgiveness and restoration because the person who had their property stolen actually benefits if they have their possessions stolen. So they are happy that you stole from them.
I have used this idea of multiplied restitution to reconcile former friends. If someone stole something or cheated or in some other way didn't pay, I have suggested that people pay double in order to restore the relationship.
Solomon is using this idea of godly justice to point out that there is no amount of restitution that will make the sin of adultery restored. The adulterer steals something that cannot be restored. They steal trust. They steal oneness. They steal affection. They steal respect. All of these things do not have an amount associated with them.
Solomon goes on to say that for the kind of violation that adultery brings, there is no adequate restoration that can make the other person happy. God's justice system is designed to be restorative if at all possible. These provisions about stealing are designed to cause people not to steal but also to bring about the restoration of the relation broken by the theft.
That is why Jesus Christ coming to earth, living the perfect life, and surrendering the perfect life for our sins was the perfect act of justice. He did that to restore our relationship with God. If we embrace the wonder of His death for us, we can interact with God without fear even though we have done many things to offend Him.