The OneToOne tool previously reported the percentage of SNPs which were identical along with the total number of SNPs used.   Additional information is now available.   There are three cases:

Here is what this section looked like in the past:

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This is what it looks like now for kits which are not the same nor parent child

The new format provides a count of the full match, half match and mismatches as well as the percentages

Aligned - is the number of SNPs which are present in both kits for the comparison

Full match - is the number of aligned SNPs which both alleles match

Half match is the number of algined SNPs which only one of the two alleles match

Mismatch is the number of. algined SNPs which have no matching alleles

The "Gen" reported for parent child is 1.

In this case there is additional information

In this case there is an additional reporting of dissonance.

Dissonance is where on the aligned SNP the alleles reported for the parent and child are not possible.

In parent child comparison since the child gets one allele from each parent there should be no aligned SNPs which are mismatches since a mismatch is when no alleles match.

Dissonance could be caused by mutations or machine misreads.

This gives some insight into the error rate of different vendor's kits.

In the case above both kits are from Ancestry and have a fairly low dissonance.

If the two kits are from the same person the "GEN" reported is 0.

Below is the reported metrics for the same person from Ancestry and MyHeritage Whole Genome Sequence (WGS)

For the same person all aligned SNPs should be the full match.   In this case half matches and mismatches are dissonant.

One can see that the dissonance percentage is much higher (almost 100x)  than dissonance of the two Ancestry kits in parent child.

Since the mutation chances are not a factor of the vendor it seems that most of the dissonance comes from machine error rates.

These additional metrics can be used to evaluate error rates from different vendors/chip sets provided there are kits which are parent child or same person kits.   This is helpful in building confidence or increasing caution when looking at matching segments.

Finally some users understandably get the wrong impression when they see a high full match percentage between two kits that this indicates a DNA relationship.   Only when there are a continuous sequence of half or full match SNPs is there reason support a DNA relationship.

With low variability SNPs might have a minor allele frequency (say below 0.05) results that almost all the alleles at this SNP are going to be the major allele with a resulting very high probability that any two kits on this SNP will be full match.   So having a lot of low variability SNPs will result in increasing the full match percentage between any kits.  It does not imply a DNA relationship.