According to the "Sterbebücher" (death records) of Auschwitz, Saomon Aäron van Kollem was murdered there on 3 September 1942. This date is different from the official date of death as determined by the Dutch Ministry of Justice after the war. For the time being, the website joodsmonument.nl, list only the dates of death, as published at the time in the "Nederlandse Staatscourant" (Dutch Government Gazette) by the Ministry of Justice.
Sterbebuch Auschwitz (death record)
Official death certificate no. 409 for Salomon Aäron van Kollom dated 25 August 1950 (after clicking the link, the website will open - just wait a few seconds and then scroll to the correct deed).