Spectrum is what
@MabuyaQ is referring to when he says color temperature. It's a scale that has long been used in aquarium lighting to give a more objective measure to the "blue-ness" of our lights. You are probably familiar with color temperatures like 6,500K, 10,000K, 14,000K, and 20,000K.
The argument being made here is that the CoralCare was designed for the European market first, which strongly prefers a "natural" 10,000-14,000K look. The full-on blue, no-white, actinics-only type reefs that are common in the US are not something that was designed for. BRS tested these lights with blues at 100% and whites at 30% to match the color temp they liked (very blue), so of course the output will be predictably diminished.