Eternity-Infinity
Eternity is that which has no beginning and no end. Infinity is that which has a beginning but no end.
God must be eternal instead of infinite. A beginning would be relative to something. The set of natural numbers (0, 1, 2, etc.) is infinite, since it has a beginning (0).
It makes sense, that the creation of God would be infinite by nature, not eternal. It's as if God is marking a spot where creation begins. And since we are still here, there is no end to creation. Our existence has not come to an end. That means our existence is in essence, endless. Thus creation is infinite.
We can, of course, draw arbitrary lines, arbitrary ends, and then measure the difference. Similarly, we take the first 100 natural numbers of the infinite set of natural numbers and measure them. Doing so we're drawing the same arbitrary line in an infinite set as with our existence.
Considering all natural numbers, we can count them up ad infinitum. We can also measure time ad infinitum, since time has not come to an end.
Having a beginning doesn't necessarily relate to space or time, but cause. If one thing causes another thing, then the other thing cannot be eternal, but is infinite. And so, the creation of the eternal God is infinite, even if creation was caused outside of spacetime. This could be explained with dependecies: if one thing depends on another, it cannot be eternal. And so, God doesn't depend on anything.