Dr. Craig is a liar.

[Angrboda]

Numbers and relationships don't exist in the natural world.  They are functions of the concept of quantity which itself is a function of the idea of an object.  In the universe at large there is only undifferentiated being.  The desk is a part of the room which also contains the chair.  None of these are distinct objects except in the conception of the mind.  There is nothing special about the substance of the desk which separates it from the air surrounding it.  We impute a distinction by virtue of the way our senses break things down into separate parts.  The parts don't really exist as parts, it's just a function of the way our senses perceive the whole.  We 'break it down' into parts because that is the way our senses work.  If we didn't have this breaking down into distinct objects, we wouldn't have the concept of quantity.  Quantity, numbers, and relationships are artifacts of the granularity of our senses.  As artifact, they don't exist as natural kinds in the universe.  That we break things down into objects and parts when we perceive them isn't grounded in God.  So quantity and number aren't grounded in God.

Would you consider yourself an anti-realist?

That depends on what you mean by an anti-realist.