We humans are finite or partial and possess only finite minds; therefore we cannot comprehend nor grasp the whole which is infinity, God’s domain. And because God Himself is infinite and not finite, He is thus whole and perfect, thereby not partial; ergo He’s uncreated in His infinity.
However, because we’re created (i.e., plucked out of infinity), thus limited, finite, and partial, we cannot fathom anything that is not created, just the way we cannot truly fathom God’s perfection because of our imperfection.
Consequently, we, finite, imperfect, and partial beings, know and understand only in part, but one day we will know and understand fully – when we are reattached to the Eternal Lord in His infinity (or eternity), from hence we came.
“For we know in part and we prophesy in part, but when the perfect comes, the partial passes away… Now we see but a dim reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully…” 1 Corinthians 13: 9,10,12