In the documentation of the example of Y splitter, when FOM_Target is set to 0.5 in the code, the illustrated figure for FOM is converging to zero (please see the attached screenshot). This shows a mismatch between what we define as Target_FOM in the code and what is being plotted as the final FOM. So, I wonder what really Target_FOM in the code is? Keeping in mind that, in the code, T_up is not defined anywhere. We only have Target_FOM.