DxOMark Lens scores

I've never looked at DxOMark to see how lenses fare until today. What do those scores mean?

I see the highest any Pentax lens got was 15, which seems poor. They have tested some quality lenses there but the highest is for the DA 35/2.4

Many Nikon, Zeiss and some Samyang lenses have scores in the 30's.

Why are these scores so different from real life?
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[url= http://www.pentaxphotogallery.com/home#section=ARTIST&subSection=2323984&subSubSection=0&language=EN]MY PPG[ url]
K10D, K-7

Pentax: DA15/4, DA21/3.2, FA31/1.8, FA43/1.9, FA77/1.8, F135/2.8, FA*28-70/2.8, FA*80-200/2.8
Sigma Zooms: Sigma 100-300 F4

'Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming... 'Wow! What a ride!'