Witte de With's letters have the answer

(Blogger seems to be getting bad again) Page 117 of Witte de With's letters gives an expanded list of Rotterdam ships that explains the earlier list:

Adm   Ship            Guns  Crew  Commander
R     Utrecht         22     98   commandeur Haexwant
R     Overijssel      24     98   kapitein Vijgh
R     Rotterdam       32    120   luitenant-commandeur Pieter Verhaven
R     Gorcum          30    116   kapitein Willem Arensz Warmont
R     Dolfijn         32    116   kapitein Kerckhoff
R     Gelderland                  kapitein Aert Jansz Jongen Boer (van Nes)
R     Brederode       56    268   Lt-admiraal Tromp's flag captain

Sources:

1. James C. Bender, unpublished manuscript "Dutch Ships 1600-1700", 2006
2. Witte de With, letters from 1653 to 1658, Archive E8811 from the Riksarkivet, Stockholm