Thinking in Afrikaans

I went to a shop yesterday and was served by a woman with a distinctly South African accent.  She made a intriguing mistake while serving me.  The cash register showed the correct change to be "£3.81" but she was about to hand me "£3.18" when she corrected herself, saying "I'm thinking in Afrikaans".   Is there something about the way numbers are represented in Afrikaans that could lead to such errors.  Or was the remark just a racist denigration of the intelligence of Afrikaners?