Depends on if you're following the iTalki lesson policy guidelines or not which can be found on this site. It does say "If a student is late, be available to teach during the entire booked lesson time. However, teachers are not expected to make up lesson time lost due to student tardiness and are not required to continue the lesson beyond the official end time." However, I've had student's whom I've formed good multi-year relationships with and will typically use my judgement. Just in case, I also take screenshots of my computer's clock and message to the student in order to prove the lack of communication if I'm ever contacted by iTalki's review board.

I am a student in two languages. I would fully understand if my tutor had signed off if I was more than ten minutes late. I can always send them a message if this is the case.

Since tutors are self-employed and italki hasn't specified any rules regarding this issue, I think it's up to you. I wait 10 minutes for a student unless they've told me that they're stuck in traffic or are having some other issue. I will also schedule a make-up lesson (outside of italki since they already paid for the lesson) IF the student has a good enough excuse (computer problems, no electricity, etc.) But I've also prepared a document explaining my cancellation policy and other things like lateness which I send to students who become regular attendees. That way I've covered my bases. However, I once reported a student to italki for not showing up for a lesson after 10 minutes and I had to fight with them to get paid for a missed lesson. Italki's support person argued with me that I should wait a full 60 minutes for a 60-minute lesson. (The student showed up 40 minutes late.) But I insisted that that was my policy and I'd already spent my time planning and opening all my files and websites, so italki eventually sent me the lesson credit.

It's about responsibility. The student should send you a message explaining why he won't show up. I would say 5 min just because we can always have delays. Even 10if you are real kind but no more than that.