According to the FB website, FB members get (cut and paste):

Economy Comfort
Silver: 25% discount on KLM
Gold: 50% discount on KLM
Platinum: free on KLM

Delta Comfort+ on Delta Air Lines flights

Silver: Comfort+ seat free of charge 24 hours prior to departure******
Gold: Comfort+ seat free of charge 72 hours prior to departure******
Platinum: Free of charge at time of booking******

Don't know the status of the OP but looking at the amount and his posts it looks he is a either a Silver or GM??

**** 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
****** 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.