The third argument, arg$3,$ is a non$-$negative integer number $($of at most $4$ digits$),$ specifying the key of the Enigma cipher. The two rightmost decimal digits $($what are called the least significant digits$)$ of this number represent the initial shift $($to right!$)$ of the inner rotor $($what we called key$\_$part$\_1$ in Enigma Operation for this PA$).$ The next two digits give the initial shift $($to the right$)$ of the middle rotor $($what we called key$\_$part$\_2).$ For example, the number $1329$ means that the initial shift of the inner rotor is $29$ positions $($which is the same as $2$ positions, as it wraps around after $27$ turns$)$ and that of the middle rotor is $13$ positions$3.$ So the following keys all result in the same starting positions of the rotors: $1302,1329,9483,$ etc.