As I understand it we assume an age of around 14bn years for the universe because this is how long the light from those objects has taken to reach us.

However if there were earlier objects emitting light we wouldn't be able to see them because the light is still travelling through space so we could actually be way off.

Now, to get a little bit metaphysical: assuming God exists outside of space and time they are not subject to its laws or linearity. They could feasibly experience every moment in time at the same time.

Imagine an infinite loaf of bread with each slice representing a period in space/time. The breadcrumbs (ie us) within each slice can only look back at what came before and theorise what will come next; they cannot see the whole loaf and may not even believe in a baker at all. The baker though can see the whole loaf at once.