They'll probably just have a choice of sandwiches, same as Y. The LCY flights are advertised as one class of service but if you book into ES you get the first few rows. As the catering is the same it means those in Y get a full drinks service too, not like the limited economy drinks service you get intra Europe on most other KL flights.

Also to compete with VLM, KL have made improvements to this route, main one is to park at the gate at AMS.