Function calculate_deferred_pool_balance_change 

pub(crate) fn calculate_deferred_pool_balance_change(
    height: Height,
    network: &Network,
    parent_chain_value_pools: ValueBalance<NonNegative>,
) -> Result<DeferredPoolBalanceChange, SubsidyError>

Calculates deferred issuance and fixed lockbox disbursements using the exact parent’s pools.