fobs_phases_freeR_flags.mtz overall_best-090903a.pdb strategy=rigid_body+individual_sites simulated_annealing=true simulated_annealing.start_temperature=8000 sites.rigid_body="chain A" sites.rigid_body="chain B"

However, the program says "
F-obs:
exptl_fobs_phases_freeR_flags.mtz:FP,SIGFP

If previously used R-free flags are available run this command again
with the name of the file containing the original flags as an
additional input. If the structure was never refined before, or if the
original R-free flags are unrecoverable, run this command again with
the additional definition:

refinement.input.xray_data.r_free_flags.generate=True

when I use phenix.mtz.dump exptl_fobs_phases_freeR_flags.mtz, it indicates that it has FreeR_flag=1. Can anyone tell me why there is FreeR_flag in my data, while the refinement program does not recognize it?
label      #valid %valid    min    max type
    H           35619 100.00%   0.00 22.00 H: index h,k,l
    K           35619 100.00%   0.00 45.00 H: index h,k,l
    L           35619 100.00% -33.00 33.00 H: index h,k,l
    FP          35619 100.00%   0.00 114.22 F: amplitude
    SIGFP       35619 100.00%   0.15   6.13 Q: standard deviation
    PHIM        35619 100.00%   0.00   0.00 P: phase angle in degrees
    FOMM        35619 100.00%   0.00   0.00 W: weight (of some sort)
    FreeR_flag 35619 100.00%   0.00   1.00 I: integer
    FC          35619 100.00%   0.00   0.00 F: amplitude