Dear Sharon,
The date of death is based on the testimony that Jannetje de Klerk gave regarding her husbands death. It is discussed more thoroughly in the booklets. Pieter Becker - n Stamvader - Sy misdade en Verhore and also Jannetje de Klerk - Stammoeder van Gouws en Bekker Families. Both booklets were published by the Hugenot Museum in Franschoek. The exact archive references are given in these booklets. In her statement she says that on the night of 26 Feb 1698 and continues to detail how her husband died.
I had a look. Both these booklets do not mention the date of birth of Andre Gouws.
Regards
Thomas