If reaching 100% of a goal is success, but it's possible to perform better than 100%, how do we calculate success better than 100%?

Question

Janise works in a call center for a credit card company. One of the ways she is measured is on how little time it takes for her to correctly resolve a customer’s problem. Her and her peers are given a target goal of 8 minutes. In other words, If their average call time is 8 minutes, they have reached 100% of their goal. However, it’s possible to have an average time better than their goal of 8 mins. After working in this job for 6 months, Janise has reached an average call time of 6 minutes. What is Janise’s percentage over target? Assume that 1 minute is the upper limit for how quickly a call can be resolved.

Answer 1

Why not just take the average time divided INTO the goal (8 min) and convert to a percentage?

Thus 8/8 is 100% and 8/6 is 133%.

In this scheme, a neophyte taking ten minutes per call, on average, gets 80% rating (8/10).