Full rated takeoff thrust (26K in your example) is achieved with thrust levers less than firewall. It is calculated purely as a product of altitude and OAT, irrespective of any derate and assumed temperature you might have set - think of it, it's the same as you get during a go-around (2nd push of TOGA), where there is no derate/assumed temperature set.
Maximum rated thrust is achieved with firewalled thrust levers. Engines can safely produce a bit more thrust than for normal takeoff/go-around operation, but that is only used during windshear and terrain escape manuevers.
Look at FCOM Vol. 2, under "EEC Normal Mode" for a better explanation.