i check a cross section file from Geant4Install/data/G4NDL4.6/Inelastic/F06/8_16_Oxygen.z, the Qvalue of oxygen 16 shown on line 3 from the file is -7161950, and the mass is 15.8575 on line 32.
if the mass of oxygen 16 is 1.4899167208E+04 MeV c-2, and the neutron mass is 9.3956533000E+02 MeV c-2, then the mass one line 32 is right, but the Qvalue should be -1.3387807200E+02 MeV on line 3.
Look at the code G4ParticleInelasticBaseFS.cc. To my understanding if the value is not valid in the file, the code calculates it.
I recommend you that you run Geant4 example Hadr03 and fill the .cc file with G4cout’s (or run with a debugger) to better understand what happens.