My bad, bad copy and paste. The 4 asteriks are related to 'a guaranteed seat in Economy', nothing the do with pref/EC/C+ seats


* for all flights with a weight concept: extra baggage allowance is 10 kg (Silver), 15 kg (Gold) or 20 kg (Platinum)
** except at Roissy Terminal 2E and Terminal 2F for non-Schengen flights
*** lounge access fee varies depending on the airport and access is subject to availability
**** on full-fare tickets booked at least 24 hours in advance and only if all classes (Economy, Business, and when applicable First Class) are fully booked
***** upon member’s request and depending on availability
****** outside these time frames no discounts apply. Basic Economy (E) fares are not eligible for paid or free Delta Comfort+ seats, regardless of elite status.
******* except for Basic Economy (E) fares, which are not eligible for paid or free Delta Comfort+ seats, regardless of elite status.

Or check here:
http://www.klm.com/travel/nl_en/flyi...all-levels.htm