I'm on your site, and read that section, and it does not tell me what the difference between a 5 and a 15 is. If you want users, don't make them read the paper itself to find out. In other words, it's not obvious what units the numbers are in.

Edit:

Tried reading paper. Still not sure. It looks like you picked an equation that divides the scores into 6 sections. the top one being 15-90 and the rest much smaller ranges. i don't understand why that division maps to "high impact" etc terms, nor still precisely what that is supposed to mean. but there's a footnote:

http://www.sciencemag.org/cgi/content/full/319/5865/948?ijke...

17. Materials and methods are available as supporting material on Science Online.

in those materials, i find a chart saying the top section means > 90% degraded ocean. so ... does that mean 90% of the water there has turned to sludge? 90% of the animals are dead? something like that? if so, that's plenty easy to understand and could be made more prominent.