You need to understand the ORDER of the "Decree(s)" as set forth historically in Systematics. The Supra system does not hold to any "passing by" of the reprobate but rather holds to a "positive" double predestination, i.e., in regard to salvation, both elect and reprobate were predestined to their respective ends before God even determined to create them and without any regard to the Fall.

Read these:

Development of the Doctrine of Predestination - Herman Bavinck

Supralapsarianism and Infralapsarianism - Herman Bavinck