The only "metacognitive" skill it needs is to know how many D there are in every token, and sum those up. Humans are great at that sort of skill, which is why they can answer that sort of question even in languages where each letter is a group of sounds and not just one like Japanese katakana, that is not hard at all.

LLM are also really great at this skill when there is ample data for it. There is not a lot of data for "how many D in DEEPSEEK", so they fail that.