Wouter Corneliss Mostert, SV/PROG2 - What is the reason for Wouter Corneliss/Cornelisz/Cornelissen listed as SV/PROG2 as opposed to SV/PROG ?

I am wondering why Wouter is listed as SV/PROG2 ?

Wouter first appears in Cape of Good Hope records in 1656 :

MUSTER ROLL OF THE OFFICERS, SOLDIERS AND SAILORS STATIONED AT THE FORT THE GOOD HOPE ON THE 20TH MARCH, 1656 (1 of 133 persons) (#61) Wouter Cornelis Mostert, of Utrecht, arquebusier

I can find no records of an earlier arrival in the Cape of a member of this Mostaert/Mostert/Mostaart family.

I would be interested to know why he is marked as SV/PROG2.

Regards,

Michele