God's action is the creature's own action as receiving its being from God, not a distinct action on the will
Next, and consistently with this, they teach that the action of the first cause concurring with the secondary cause is not an action really distinct from that of the secondary cause. It is that same action, considered as receiving its being from the first cause.
So when God concurs with the will in an act of willing or refusing, he does not, on their view, exert on the will an action distinct from the will's own. He only gives being to the will's action together with the will, and keeps that action in being. God's cooperation here is therefore not something other than our act of will; it is our act of will itself, insofar as its production and preservation depend directly on God.
Latin
XXVIII. Deinde consequenter docent actionem causae primae concurrentis cum causa secunda, non esse actionem reipsa diversam ab actione causae secundae, sed illam ipsam actionem, quatenus esse suum a causa prima accipit. Ita quum Deus, verbi causa, cum voluntate concurrit in volendi, vel nolendi actu, ipse non exerit, ex eorum mente, actionem aliquam in voluntatem, distinctam ab actione voluntatis ipsius; sed tantum esse confert actioni voluntatis simul cum voluntate, & actionem illam conservat. Ac proinde divina hac in parte cooperatio non est aliquid diversum a volitione nostra, sed ipsa nostra volitio, quatenus a Deo immediate pendet quoad sui productionem & conservationem.