The skill levels of each team member, allows you to define if a member has or not a skill and what his level is.
When the cursor is set completely to the left side, it means that the member doesn't have this skill.
Setting the cursor in the middle means that this team member will deliver the work of a task having this skill at the exact estimations indicated.
If you set the cursor lower or higher, the member will be slower or faster delivering a task needing this skill.
The prediction engine will take these settings into account and calculate, with the Skill's estimation factor in how much time each task can be performed by each team member and decide who's the best suited for the job (depending also on team members availability).
When adding new skills, the added skill is added to each team member but indicating by default that they don't have this skill.