Math came from us; it's the 'language' we use to accurately interpret the nature of our reality, from 2+2 = 4 to δqrev/T = ΔS, and well beyond. Because we understand and interpret our reality through these 'languages' of course our reality can have the surface appearance of being 'written', but that doesn't make it so.
What you're really asking, and correct me if I'm wrong, is where does the nature of our reality come from; how did the parameters themselves come into being, or more fundamentally, how did 'something' come from 'nothing'. The incredulity surrounding the 'big bang' centers around this premise; how could it possibly be- outside of Scripture of course- that all the universe and the forces that rule it just spring into being out of nothing?
The thing is, and this is a weird concept to wrap one's head around perhaps, 'nothing' is just an abstraction, and there's no evidence that it exists in nature. Open an empty box, and you can fairly say 'there's nothing in this box.' And that's the abstraction at work. In reality, of course there's lots in that box. There's a space, there's a volume of air within that space, there are particles within that air, tons of stuff. Leave the atmosphere, launch yourself up into space, and open the box there, you can still fairly say 'there's nothing in this box.', but again, that's just the abstraction of the word, for there's space in that box still, and space in which that box can exist, and space itself IS something. It's theorized with some mathematical accuracy that beyond all space in the 'quantum void' of the universe, there would still be quantum particles blinking in and out of existence constantly, even in the absence of space, even in the absence of
time. That's another concept which boggles the mind; that things can exist or 'occur' independent even of time, but time is just another malleable force of nature, inexorably tied to and influenced by space and forces like gravity, and even in the absence of all these things, it's not 'nothing' that remains.
https://scratch.mit.edu/projects/133691221/ this is a cool little 3D program that randomly generates a snow-flake. The mathematical principles that generate the snowflake in the program are generally the same as those that produce the snowflake in nature. So ask yourself: is the snowflake that forms in real life produced by the 'computer program' of reality?
DNA does indeed carry the biological information which distinguishes one organism from another, and we map and model that information as a language, a 'code', much as we do with all things in nature we endeavor to understand scientifically. DNA thus begins to seem very much much like a 'computer program', and thus can easily be presumed to have been 'written' into existence. That's projecting our method of interpreting and understanding DNA onto its nature though, and is no different than claiming any other complex natural process which requires a language to interpret/represent must be 'written' into the world. DNA is 'like a computer program' in the same way that a brain of any creature is 'like a computer', but these are just analogies, and clearly no brain is built or designed.