The AFM will (usually) have separate performance chapters for rated TO (identified by the engine model), plus one or two derated TO (-10, -20, etc.) chapters. Any of these may be used given appropriate TOGW, r/w available, ambient conditions etc.
If you derive your FLEX TO data from one chapter, the max thrust you can safely use after a V1 cut is the N1 or EPR FROM THAT CHAPTER. (Albeit JT points out some additional pre-TO checks you can make...)
Does this help?