The DNA Clans database compares your Y-DNA STR markers (not SNP markers) to the profiles of ethnic and indigenous populations to find out which indigenous populations and places in the world match the compared Y-DNA STR markers the most.
For example, if you have the Y-DNA STR markers DYS19a, DYS389i, DYS389ii, DYS390, DYS391 and DYS393 it matches to 420 indigenous populations in 21 publications indicating that your closest paternal match is to the Cabecar on your direct paternal lineage (your father’s father’s father’s… line). Once determined, your Y-DNA STR markers will never change and will always remain the same.
The populations are ranked in the order of most similar to least similar to your Y-DNA type. The number beside each population is called RMI (Relative Match Index). RMI number is generated in order to compare the populations in the search against each other. You must compare the RMI numbers against each other.
For example, if the RMI of the Cabecar population is 22.80 and the RMI of Danish (Copenhagen) population is 12.73, then you are more similar to the Cabecar population with the RMI of 22.80 than the Danish (Copenhagen) population with RMI of 12.73.
Please note that if your Y-DNA is matching at highest frequency with populations from the Cabecar, it does not necessarily mean that you or your ancestors are Cabecar, but it does indicate that other individuals whose genetics are most similar to yours are present at the highest frequency in Cabecar and that your Y-DNA profile is more similar to the individuals from the Cabecar population study than to other populations in the comparison.