Hi! Clozemaster newbie here, still figuring things out.
I haven’t changed the default review intervals yet, so it looks like a 100% mastered sentence would return for review in 180 days. But I noticed that the check mark button for manually mastering a sentence in the app shows a review interval of 
- and the confirmation message says the next review date is set to next century. Is this correct, that the manually mastered sentences won’t reoccur and the ones reviewed 4x will?
Grazie!
Essentially, yes. The “known” button is intended to be used for a subtly different reason.
There are some questions that you don’t ever want to see again. Sometimes the questions may be a bit gross, more commonly the sentences are so basic that when your language learning reaches a certain point you will NEVER forget the word, and continuing to review it adds no value.
There used to be an “Ignore” button for that, but the problem was that it screwed around with your progress scores. The replacement was the Known button.
This is different to something that is simply “mastered”. With less common words, you can “master” them but still forget them over time. They still need to be reviewed. They’ll pop up again in 180 days or whatever you have the “mastered”/ 100% review cycle set to at the time. “Known” is for words that you will NEVER forget, and there is no point in reviewing them further.
EDIT: I should add… if you ever reset the collection that the known sentence appears in, it WILL go back to being a “normal” question and will go back into the normal review cycle.
What you correctly describe is the difference between “100 % mastered” and “known”.
The system never sets a cloze to “known” automatically, that you will have to do manually.
Of course, “known” includes “100 % mastered”.
I normally set clozes to “known” after the first 180 day repetition (“100 % mastered plus one)” and if I have no problems remembering and can answer the cloze instantly.
But that’s a personal choice.
I must say I prefer the web interface, even on my cell phone, because I can freely add new clozes from existing ones, and I can comment. That said, the app has more flexible next-review-date controls.
However, when I recently used the Android app, in offline mode, I noticed that the app’s check-mark button works differently than in the web version: it immediately sets the cloze to “never see again”, whereas in the latter it merely sets it to 100% complete. I must say I prefer the more conservative approach of 100% complete, and would very much like to have two separate buttons. Now I found myself repeatedly awkwardly setting the percentage to 100.
I usually don’t dismiss a cloze completely on first sight, unless it’s a variation on an already known theme, not until I have let it pass at least one review cycle. Maybe that’s why my review queue is so long? 
Update: I should add that I use the app’s Clozemaster Radio a lot.
Just out of interest, I always work on the android app and pop over to the Web version for Discussion. This is solely to avoid the dreaded white key strip when typing in text on the Web version😐
I’m not familiar with the dreaded white key strip - sounds ominous! I‘ve only been working in the app so far. I do like the ability to use the app offline where there’s poor reception (although I’ve learned not to do listening exercises while offline).
It’s nothing too serious, just a bit annoying. Probably something to do with a Google password saving feature I can’t get rid of. The variation in learning that ClozeM offers is amazing, it’s certainly improved my Italian and I greatly appreciate the more adult approach.
