Results of the injection-recovery experiment performed with MATRIX to assess the detectability of the candidate TOI-521 c. The colour scale represents recovery rates, where bright yellow indicates high recovery and dark purple or black indicates low recovery. The solid blue line marks the 90% recovery contour, the dashed white line indicates the 50% one, and the solid white line shows 10%. The white dot marks the nominal value for TOI-521 c derived using spright, and the solid green line denotes the 95% credible interval of the most probable radius distribution.