From Yuku Help

Auto titles

This section is where you set the titles - or levels/ranks - that are automatically applied to your members. You can set up your titles to be applied according to various criteria.

You can set automatic titles on post count, length of membership, and kudos. You can also set titles for your moderators and admins on this page.

A member can have more than one auto title, if more than one auto title applies to them. For example, they might have a auto title due to having more than 50 posts, and also an auto title due to being a member for more than 12 months.