I was wondering if the five turn countdown until Regigigas is at full strength is five turns he is in battle or five turn in general.
Slow Start causes the Attack and Speed stats to be halved during the first five turns in battle. This counter is reset if the Pokémon is switched out. If this Ability is replaced due to a move like Skill Swap or Worry Seed or is suppressed, the Pokémon's stats return to normal. In the Japanese version of Pokémon Diamond and Pearl, removing Slow Start does not undo the Attack and Speed drop; it must still wait five turns. This was changed in localized versions as well as in Pokémon Platinum. If the user holds a typed Z-Crystal and uses a Z-Move based on a special move, Slow Start will also reduce the Special Attack stat for the duration of that move only.
Slow Start causes the Attack and Speed stats to be halved during the first five turns in battle. This counter is reset if the Pokémon is switched out.
If this Ability is replaced due to a move like Skill Swap or Worry Seed or is suppressed, the Pokémon's stats return to normal.
In the Japanese version of Pokémon Diamond and Pearl, removing Slow Start does not undo the Attack and Speed drop; it must still wait five turns. This was changed in localized versions as well as in Pokémon Platinum.
If the user holds a typed Z-Crystal and uses a Z-Move based on a special move, Slow Start will also reduce the Special Attack stat for the duration of that move only.
In Legends: Arceus, Slow Start isn't an Ability, but a status condition exclusive to Regigigas. This status condition functions the same as the Ability.
Source
