Are you sure it was actually booking class that you saw? On a recent flight, the FA claimed that he did not have our meal orders on his manifest but later figured out his mistake by looking at his handheld device, which clearly showed a knife and fork symbol and green color symbol on our seats on his device. He actually showed us his manifest and his handheld device telling us what each of the codes/symbol meant. I do recall seeing some letters that resembled booking classes but he explained that they meant something else, like connections, etc. Could that have been what you saw? He also said that the paperwork they get is often not accurate and handwritten by the gate agent and tell future FAs to look at their tablet if in doubt.