The existence of knowledge and the external existence of its object are distinct questions.
Knowing a possible thing does not require that it already exist. Something that will be created later is not yet actual, yet it is not beyond divine knowledge. An impossible proposition can also be known as impossible; its being known neither makes it possible nor brings it into existence.
1. Existent: something presently actual.
2. Nonexistent but possible: something that could exist but does not yet.
3. Impossible: something that cannot obtain because it entails contradiction.
Therefore, not everything known is existent, and the scope of knowledge must not be measured by the number of existing objects.