OM = Other Metagame
>What is Hidden Type?
The Pokemon's Hidden Power type will be added to its type(s), if it does not have that type. For example: if Heatran has the IVs for Hidden Power Flying, its typing becomes Fire/Steel/Flying and if Chansey has the IVs for Hidden Power Ghost, its typing becomes Normal/Ghost. However, if Dragonite has the IVs for Hidden Power Flying, its typing remains Dragon/Flying. This means that if you do not change the IVs, Dark type will be added by default and if you do not want a type to be added, the IVs should be set for Hidden Power to be one of the Pokemon's types.