How do I create multiple one-to-one meetings with different durations and open dates

I’m using Calendly in a volunteer project, where I need to schedule 90 minute meetings, as well as for personal 30 minute one-to-ones. I set up the 90 minute meetings/dates/duration, then tried to set up the 30 minute meetings. Those defaulted to the dates/times I had set up for the 90 minute meetings.