Details about MZM Analytical

The operation of the MZM is described by the equation shown below
Eout (t) = Ein(t).cos(∆θ(t)).exp(j.∆φ(t))
where the difference in phase between the two branches is given as :
∆θ(t) = π
2 .(0.5 − ER.(Modulation(t) − 0.5)).
The parameter ∆φ is the signal phase change described by the
following equation:
∆φ(t) = SC .∆θ(t).(1 + SF )/(1 − SF )
where SC = -1 if the negative signal chirp is true and is = +1 if the
chirp is false, SF represents the Symmetry Factor and Modulation(t)
stands for the incoming electrical signal that has a normalized value
lying between 0 and 1.
These equations are given in the component help of MZM Analytical in Optisystem. Can someone please explain the significance and meaning of the terms
Modulation(t), SC and Symmetry Factor in the given equations.