ChatGPT Long Term Memory limit

How does the ChatGPT4o paid long term memory work? By words, characters, kilobytes? It is so annoying to manage. You have this human like computer entity and need to manage this few thousand word memory system worse than an early 1980s 720 KB 5.25 disk drive. It is regularly filling up. I need to delete important memories. Have ChatGPT consolidate memories to save words. What the hell is this and when are they going to make it better?