Testability explorer will use a weighted average for its cost aggregation. The formula for this will use an exponent 1.5 to do this. Thus an normal weight calculation would be sum(value^(1+1.5)/sum(value^1.5). By setting this option to a value different from 1.5 you can tweak the weighted average. Remark setting the factor higher than 10 usually makes no sense, as your average will be reasonably close to your maximum cost. If you set it too high you'll end up having 0 as cost due to overflow!