"Let light be, and light was" is normally translated as "let there be light, and there was light." We (that's me and the Holy spirit) develop the logic of how God caused light to appear.
Let Light Be Nucleosynthesis
The Traditional Understanding of “Let there be Light”
The first major split between Matty's Paradigm and Creationism is in answering the question: What's the source or nature of the light that the Lord created on the first day of creation?