Data/model ratio for the Athena/X-IFU spectra of PG 1211+143 at low (top), middle (middle), and high (bottom) states with an exposure time of 10 ks. The simulation of spectra is based on the best-fit continuum model, with the UFO ionization state predicted by the fit (see Table 3) and normalization adapted to reproduce the luminosity indicated in the legends. The UFO velocity is assumed to follow the trend of I ZW 1, instead of the constant trend of PG 1211+143, to simulate the change in UFO velocity. The vertical dashed green lines present the blueshifted UFO absorption features at different states.