Pull Assigner lets you choose from two different algorithms for assigning reviewers.
The load balance algorithm assigns reviews based on who has had the least number of reviews requested within the past 30 days (or since "Reset stats" was last clicked). The algorithm takes into account all review requests, not just ones requested by the Pull Assigner bot. This algorithm is well-suited for teams that want to equalize the number of code reviews done by each team member.
The round-robin algorithm assigns reviews in circular order, regardless of how many reviews each team member has had requested in the past. This algorithm is well-suited for teams that are interested in getting pull requests looked at by different people across the team in order to spread knowledge and get diverse opinions.