On page 218 Aletta Maria Muller - b1c6d4e6, ≈ 5 10 1794 x Graaff-Reinet 2.5.1813 is stated as having married Anthonie Michael Muller.
On page 253 Maria Muller, d1e1 Aletta Maria b1c8d1e1 is also stated as having married x Graaff-Reinet 2.5.1813 Anthonie Michiel Muller ≈ 24.3.1771, burger Swellendam ✝ Uitenhage 21 1 1843 s.v. Cornelius Johannes Muller and Susanna Elisabeth Ferreira.
This person b1c8d1e1 Maria is incorrectly listed as Aletta Maria on page 253. The relevant baptism clearly has her as Maria.
To add to the confusion Maria's sister b1c8d1e7 is Aletta Maria Potgieter b1c8d1e7 ≈ 31 10 1790 ✝ 1825 x Cape Town 20 4 1808 Thomas Ignatius Ferreira ≈15 4 1787 ✝23 3 1843 (56.4) s.v. Ignatius Petrus Ferreira and Susanna Elisabeth Ferreira. She has in the past been merged with her sister who had been listed as ALETTA Maria in line with the incorrect SAG entry
This marriage entry needs to be seen to verify but it would seem that the link to (Aletta) Maria as b1c8d1e1 is probably incorrect.
Calling Private User and Private - who may know where to locate the marriage entry.