How are Supererogative acts even possible in Catholicism?

God, through each person of the Holy Trinity, the Prophets, the Saints, and his people set out what to do in order to enter the kingdom of heaven through the commandments, through the beatitudes, though lives worthy of imitation (in the case of Jesus and the Saints) and building the kingdom of God (e.g. as specified in Matthew 25). Obviously the list is not exhaustive, but suffice to say, there are clear duties set, and reasons as to why these duties help build the kingdom of God. Those who thoroughly practice the Catholic faith strive to go beyond the minimum duties [through the forces of Grace](https://www.catholic.com/tract/grace-what-it-is-and-what-it-does) . Striving for the minimum understandably does not help much for a relationship with God, and thus it makes sense to go beyond "what the instructor specifies" so to speak. But if God, who is the perfect instructor, lays out what to do for us to become perfect [and thus be able to enter the kingdom of heaven](http://www.vatican.va/archive/ccc_css/archive/catechism/p123a12.htm) , why must we go beyond what a perfect omnipotent being guides us to do? I am struggling to understand why [Supererogation](https://en.wikipedia.org/wiki/Supererogation) is a thing. Aren't those who follow God's law, in both spirit and letter already desiring to become perfect? How can we go beyond what God commands? How can one go beyond desiring to become perfect? I feel I am missing something here, but I hope readers understand my logical conundrum here.