Memory not released even after postgres table dropped

Hello. Project ID: 6dee0732-68aa-4ae0-a472-7d02880e238a I created a table on 19th August and then dropped it. I don't quite remember the name of dropped table but it was clone of api_article table at that point of time. I could see a corresponding increase in memory usage (as expected). But even after two days, I see that the memory has not been released (not expected) - screenshot attached Please suggest. Maybe I am missing something obvious.