Are you right Guy? The NEC I've seen reads 'on completion of 24 months as an employed FO and achieving a total of 2501 easyjet factored block hours the FO will be promoted to SFO'.
So if it's the NEC that DEP's expect then they will be employed as a SO and after 12 months and 1251 hours they will become a FO and after 24 months and 2501 hours a SFO.
Of course there may be a different offer on the table that I'm not aware of.