Is Solana slot time 400 ms or 800 ms?

Why is Solana's slot time is longer than planned 400 ms? solana slot context : An RpcResponseContext JSON structure including a slot field at which the operation was evaluated value : The value returned by the operation wow slot 989 SlotHistory: Holds an array of slots available during the most recent epoch in Solana, and it is updated every time a new slot is processed

password slot slot # The period of time for which each leader ingests transactions and produces a block Collectively, slots create a logical clock Slots are ordered