From BMC Biology:

Patterns of African and Asian admixture in the Afrikaner population of South Africa N. Hollfelder1†, J. C. Erasmus2†, R. Hammaren1, M. Vicente1, M. Jakobsson1,3,4†, J. M. Greeff2*† and C. M. Schlebusch1,3,4*† Abstract Background: The Afrikaner population of South Africa is the descendants of European colonists who started to colonize the Cape of Good Hope in the 1600s. In the early days of the colony, mixed unions between European males and non-European females gave rise to admixed children who later became incorporated into either the Afrikaner or the Coloured populations of South Africa. … Genealogical records previously estimated the contribution of non-Europeans into the Afrikaners to be between 5.5 and 7.2%.

Afrikaners have pretty good genealogical records, so it’s long been known that they tend to be single digit percentages nonwhite by ancestry.

Results: To investigate the genetic ancestry of the Afrikaner population today (11–13 generations after initial colonization), we genotyped approximately five million genome-wide markers in 77 Afrikaner individuals and compared their genotypes to populations across the world to determine parental source populations and admixture proportions. We found that the majority of Afrikaner ancestry (average 95.3%) came from European populations (specifically northwestern European populations), but that almost all Afrikaners had admixture from non-Europeans. The non-European admixture originated mostly from people who were brought to South Africa as slaves and, to a lesser extent, from local Khoe-San groups. Furthermore, despite a potentially small founding population, there is no sign of a recent bottleneck in the Afrikaner compared to other European populations. Admixture amongst diverse groups from Europe and elsewhere during early colonial times might have counterbalanced the effects of a small founding population.

The sample size is only 77, but here are the details:

In addition to European ancestry (mean of 95.3% SD 3.8%—blue cluster), Afrikaners have noticeable levels of ancestry from South Asians (1.7%—orange cluster), Khoe-San (1.3%—red cluster), East Asians (0.9%— purple cluster) and West/East Africans (0.8%—green cluster) …

The typical admixture date was estimated to be 1681.