The title is misleading. The maths explained in the blog is the math that is used to build an LLM (how it internally does calculations to do inference etc.). The math to understand LLMs, i.e. that explains in mathematical rigor why LLMs work, is not fully developed yet. That is what the LLM Explainability is about, the effort to understand and clarify the complex, "black-box" decision-making processes of Large Language Models (LLMs) in human-interpretable terms.