The author is offering 1.5 hours of meetings, as three 30 minute conversations. It's not nothing, but it's also probably not really the level of mentoring that can be super impactful. But it might make a difference to some people who apply.

I've had one amazing career-related mentor in my life. He probably spent 20+ hours per week for 6 months doing mentoring things for me. He worked VERY hard at this but his work was very impactful on me and I really appreciated it. He had support of his management, which was critical to being able to spend that much time on mentoring.

I've tried to be a mentor for Google Summer of Code before. It was difficult for me and required a LOT more effort and time than I had expected. Mentoring well is not easy.