No. You can teach 1 hour a month or 160 hours. It's completely up to you.
However, once you have a confirmed session you are expected to attend. Failure to attend a confirmed session will be deemed as a Missed Session which negative impacts your rating and ranking in the Find Tutor page. Too many Missed Sessions may result in your account being suspended and/or terminated at the discretion of the administration.
If you are receiving bookings during times you are not actually available then you should review your availability schedule on your My Availability page and adjust it as necessary to time slots you are available.