UnarXived Superconductivity

In arXiv:2201.11883v1 the authors Dias and Salamat define a procedure for background subtraction of experimental measurements of ac magnetic susceptibility that they call “User defined background method 1”, or “UDB_1”. They explain that they “use the temperature dependence of the measured voltage above and below” the critical temperature “and scale to determine a user defined background”, that is subtracted from the measured voltage to obtain the “superconducting signal”.

I don’t understand what that means and how it is implemented. I would like to invite particularly experimental colleagues to share their understanding of this and their opinion on whether it is a proper way to deal with experimental data.