614/621 I would say they are referring to the lift (valve) of the camshaft. It should actually be 0.614" and 0.621"
Some people also quote the advertised duration of the cam. Most will talk in duration at 0.050" ('at fifty thou')
The duration is one part of the equation but the LSA (Lobe Separation Angle) comes into it as well, PLUS the lift. Then you have the head gasket thickness, what heads, etc.