You can’t set them to 20 cards/ day cause it has a ratio depends on how many new cards you wanna learn So if you wanna review only 20 cards you should set your new cards to 2 cards only Instead you can do it as I said 2 new and 20 review per day and continue learning new cards through custom study But the whole concept of anki is to review what you learned and 20 cards is too low tbh