This is what we call a recLOH. It occurs by a mechanism that is different from the usual one (called slippage). It occurs only on multi-copy markers, such as DYS464 and DYS385. A section of DNA is deleted and repaired by copying a nearby section. They can be recognized when one value (called an allele)is deleted and a second copy of another allele appears. In his case, 12 was deleted and 14 was copied.
It occurs in 1 step so it would count as 1 mutation for Genetic Distance at FTDNAHowever, I do not think they have updated the counting method on their pages, yet. They will eventually count all mutations on multi-copy markers as 1 regardless of the difference.
with a distance of 2 and the same surname, you are probably related within a genealogical time frame, although this would depend on the number of marker tested. However, there is no real way to tell how closely you are related. Distant cousins can mismatch on fewer markers than close cousins.