SysPhS-1.1: p.57: GOTCHA: Table 11.3.2.5 Mathematical components: Mathematical.Subtraction maps to Math.Add (in Modelica) and Sum (in Simulink)

In Modelica, the Add block has weighting parameters k1 and k2, which you can use for subtraction.

In SimulLink, a special additional operator string is used on the Sum block.