I am using gpt-4o-mini: Scenario 1: I have more than 5672 (includes system prompts, tools, user messages) tokens and upon sending same request multiple times finding 5432 tokens cached, I would expect all tokens get cached, why is it lesser number of tokens getting cached? Scenario 2: if I remove a word from token and sent the request subsequently, the cached tokens are reduced more than 1000 tokens compared to its previous request, can someone explain how exactly this prompt caching works ? ...