At first, since there are two series of reactance: saturated and unsaturated in my opinion x"d saturated it is the minimum reactance in order to calculate the maximum short-circuit current.
From ANSI Standard C37.010- see:
a 2 MVA X/R=25 but for transformer of same 2 MVA rated X/R=7.5.
This ratio, for generators, refers to synchronous reactance. See: