This is a girl not a boy.
SAG shows the child's name as Cornelis Johannes, but it is wrong.
The Doopregister for this child at Uitenhage on 27 December 1817 shows quite clearly that HER name was CORNELIA JOHANNA.
The record can be found here: https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSV8-7SGD-V?i=210&...
Birth date, names of parents, and birth order (ie e1) are correct.