The Hexacoto

On a whim, I took one of those online colour tests challenging one to see how well one can discriminate colour hues. This is what I got:

However, when I submitted my score, age, and gender to see how well I fared against those in my gender and age group, this is what they reported:

How does one get a score of -332? Does that mean a better-than-perfect colour acuity? Do they perhaps see more hues than human can? Maybe they’re secretly mantis shrimps.