or:
The genetic makeup of an ethnicity is made up by the ratio of various ancient populations.
The company decides which numerical ratio is to be assigned to every ethnicity (Ethnic Average).
If the value/number of a population is a bit higher of the ethnic average, they’ll add the extra % of that population in the final results by itself.
It can also depends on how far back in time a Company does the test.
Bear in mind that over half the World's population, at one time or another, they were all in Asia Minor, most left, some didn’t or they didn’t go far. (Minestrone :)