The stars and the % number indicate the estimated current performance level, based on the predicted probability of correct pronunciation of that skill. The current performance number changes constantly as skills are acquired and as exercises become more difficult. See also How-is-performance-measured
Your current skill level is indicated by a system of stars.
One star is less than 25% current skill level
Two stars is less than 50% current skill level
Three stars is less than 80% current skill level
Four stars is greater than the current skill level set for above 80%
You will gain stars as your skill levels increase!