Set it to something like 100 new cards per day. This way, you'll be reviewing the cards you have that are due on previous days while only adding a maximum of 100 new cards a day. If you feel like that's too much or too little, you can change it.
Anki won't show you a card until it is "due" or if it is new. I believe the reason you see zero cards remaining is that your easy interval is 4 days, which means after you consider a card easy, it won't show you that card again until 4 days later.
For my own non-MCAT studies, I use a step interval of "2 10 30 90 360 720 1440 2880." This allows for me to see a card within 2 minutes if I do not know it, and if I consider it "good," I see it again in 10 minutes. If I consider it good again, then 30 minutes, then 90 minutes, etc. If I consider the card "easy," then I have my easy interval at 2 days so I don't see it again for another 2 days.
Let me know if you have more questions.
Kevin W, MCAT Tutor
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