Burn A Rogue
Unremarkable People
Have exponent 3 in all appropriate skills.
Trained Professionals
Have exponent 4 in all appropriate skills.
Experts
Have exponent 5 in all appropriate skills. It is unlikely they have a grey shaded ability, and no more than one.
Heroes and Gods
Might go beyond the expert level. They might even have one or two shaded abilities.
The Weak
Children, the frail, and the elderly might have exponents lowered by 1.
Mixed Skills
For a one-off NPC with multiple skills, their primary skill is exponent 5, their secondary skill is exponent 4, and other skills are exponent 3.
Based on the Burning Rogues rules from Burning Wheel Gold Revised (p. 562).