Normally only Concealed Kongs are considered as concealed triplets (and comparable with concealed Pungs), but Four Winds lets you specify alternative interpretations.
E.g., you can choose an option according to which Concealed and claimed Kongs are acknowledged as concealed triplets (comparable with concealed Pungs). This option is used in Chinese Classical and Chinese Official (mainland) rules. The idea behind this interpretation is that the set was actually a concealed Pung at the time of the declaration, as opposed to a situation where a self-drawn tile is used to convert a melded Pung into a melded Kong.
Note: If this option is used, the claimed Kongs are melded by turning the fourth (claimed) tile face down, as shown above.
More common option is to accept All Kongs as concealed triplets (and comparable with concealed Pungs). This alternative is often used in modern Chinese Mah Jong, e.g. in Chinese New Style. The idea behind this interpretation is that in any Kong at least three tiles have been self-drawn from the Wall.
Note: The selected option has effect on the way scoring is applied for hands requiring concealed triplets (e.g., Three concealed triplets). Notice however, that the scoring patterns Concealed hand, Fully concealed hand, Exposed hand and Fully exposed hand, and the limit hand Hidden Treasure each have a separate option which lets you specify how Kongs are interpreted. For more information, see the FAQ topic What is a concealed hand?
Kongs Hiding concealed Kongs
Kongs Declaration of Kong