How do they work exactly??? When I take a drill after learning a certain thing, it gives me around 100-200 questions on past things. And sometimes while I'm taking these 200 drill questions, the number of questions grow!! (On the Now part, not on the today, week, etc.)
I mean, I guess it really isn't a problem, I mean it is sticking in my head for sure, after bing asked 1000 times haha. I kind of like it.
But I was just curious??
I might not be one of the support staff, but I might be able to answer your question.
As you already noticed, after taking a lesson, some drills get added to the pool of drills available to you to practice the contents of that lesson. Each successful answer pushes the next occurence of this individual drill further into the future.
A quick example:
Let's say you have a drill today and answer it for the first time today. This will cause the question to get a streak of two and to reappear again after, say, 20 hours. Once this timer expires, it will be due "Now", answering it correct then will set the streak to three and the drill expiration forward for 40 hours, then, 4x and 80 hours, then 5x and 160 hours and so on. A wrong answer will reset your streak on that drill, causing it to be asked again "Now". So things you remember well should be asked less often than things you have not fully memorized yet.
An increasing number of drills in the "Now" category means that an increasing number of drills have reached their expiry time. You can take a look at your drills and their streak and expiration time at https://www.nihongomaster.com/drill/details
Hope that helps.