Fittings of the (XX − YY)/I intensity ratio, to determine polarization percentages and polarization position angles. Data presented in this figure are self-calibrated ALMA observations of the Sgr A* at band 9. XX and YY are intensities of the two orthogonal polarizations in the receiver frame. Top left: ALMA 12 m-Array observations at passband setup-c (Table 1). Top right: ACA observations at passband setup B9-a. Bottom left: ACA observations at passband setup B9-b on UTC 2015 July 25/26. Bottom right: ACA observations at passband setup B9-b on UTC 2015 July 26. The best fits of polarization percentage (P), polarization position angle (in the receiver frame, i.e. Ψ − φ; PA), and a constant normalized Stokes Q offsets (Q offset), are provided in the upper left of each panel, which are represented by a black curve. For each observed frequency, errors of fitted quantities were determined by one standard deviation of fittings of 1000 random realizations of noisy data (details are in Sect. 3.2). Gray lines in each panel plot every 100 of the random realizations. The ACA observations at setup B9-b only covered a small parallactic range, and therefore cannot provide independent constraints on P, PA, and Q offset. Nevertheless, the observing UTC time and observing frequency of the two epochs of setup B9-b observations, are close to those of the setup B9-a observations, so may serve as consistency checks. We overplot in blue the best fit of the setup B9-a observations of ACA, to the panel which presents the setup B9-b data (bottom left and right panels).