peristaltic pump

Hello,

I have some question about peristaltic pump the model Comsol, "peristaltic_pump.mph (Model Library Path: COMSOL_Multiphysics / Multiphysics / peristaltic_pump) ".

(a) The Comsol use this equation "netflow=netflowt-(inflow+outflow)/(2*Ttot)", but the correct definition of the net flow would be this equation "netflow=netflowt -outflow + inflow " ? Why of this division (2*Ttot) ?

(b) What would the value of the flow pumped by the end of a cycle?

b.1) Would be the integral outflow over time?
or
b.2) Would be the integral netflow over time?

Thanks