From:Secret Admirer

since u probably know, what is the green check?

Sorry for the late reply! Regarding your question, the green check is the mark of being a 'Verified Author'. I've answered this in another letter as well (I'm gonna copy and paste the answer here~), but for now there's no actual actual way to get verified other than being a beta tester. This system is still currently being worked on by the developer. I will help to raise this issue, but other more precedent and pressing issues and features will take priority! Thank you for your question~