Look at documentation of "Specified combinations".
"If more than one parameter name have been specified the lists of parameter values are interpreted as follows: Assume that the parameter names are p1 and p2, and that p1 has the list 1 3 and p2 has the list 2 4. For the Specified combinations sweep type, the solver first uses p1 equal to 1 and p2 equal to 2. Thereafter, it uses p1 equal to 3 and p2 equal to 4. And when the sweep type in All combinations, the solver uses the following order for the parameter combinations: 1 2, 1 4, 3 2, and 3 4.
"If more than one parameter name have been specified the lists of parameter values are interpreted as follows: Assume that the parameter names are p1 and p2, and that p1 has the list 1 3 and p2 has the list 2 4. For the Specified combinations sweep type, the solver first uses p1 equal to 1 and p2 equal to 2. Thereafter, it uses p1 equal to 3 and p2 equal to 4. And when the sweep type in All combinations, the solver uses the following order for the parameter combinations: 1 2, 1 4, 3 2, and 3 4.