Time evolution of coronal quantities during disk passage of NOAA 12673. (a) Free magnetic energy (E_F) and (b) total helicity (H_V). The black line represents a fitting to the values computed from qualifying NLFF models (squares) onto a uniform time cadence (12-minutes). Solid and dashed vertical lines mark the GOES start time of X- and M-class flares, respectively. Blue and red color indicate the flare type (confined and eruptive, respectively).