Function prune_missed_finalized_entries 

pub fn prune_missed_finalized_entries<Block, B>(backend: &B) -> Result<()>
where
    Block: BlockT,
    B: AuxStore + HeaderBackend<Block>,

Delete entries for blocks that are already finalized, reclaiming any whose prune was never observed — e.g. blocks finalized while the node was down, which the freshly-subscribed notification stream never sees. Run once at startup, before the backfill loop.