UpdatedBestFinalizedHeader: PlainDescriptor<
    {
        grandpa_info: {
            finality_proof: {
                commit: {
                    precommits: {
                        id: FixedSizeBinary<32>;
                        precommit: { target_hash: FixedSizeBinary<32>; target_number: number };
                        signature: FixedSizeBinary<64>;
                    }[];
                    target_hash: FixedSizeBinary<32>;
                    target_number: number;
                };
                round: bigint;
                votes_ancestries: {
                    digest: DigestItem[];
                    extrinsics_root: FixedSizeBinary<32>;
                    number: number;
                    parent_hash: FixedSizeBinary<32>;
                    state_root: FixedSizeBinary<32>;
                }[];
            };
            new_verification_context?: {
                authorities: [FixedSizeBinary<32>, bigint][];
                set_id: bigint;
            };
        };
        hash: FixedSizeBinary<32>;
        number: number;
    },
>

Best finalized chain header has been updated to the header with given number and hash.