Why the two turnover numbers differ
One-way turnover is half the sum of absolute changes in every holding weight, including cash. In the default example, changes are -10, +10, +10 and -10 percentage points. One-way turnover is therefore 20%. Before funding fees, stock purchases plus sales total 30% of portfolio value: the 10% cash reduction funds the extra purchase. At a 20 basis-point stock trading cost, $300,000 gives a $600 first-order estimate.
Funding the fee from capital
The target weights refer to capital remaining after fees. The engine solves c = rate * sum_stock(abs((1-c)*target - prior)), where c is the fee as a fraction of starting value. The default becomes c = 0.002 * (0.3 - 0.4c). Stock notional is $299,760.19 and the fee is $599.52. This is a self-financing arithmetic convention, not an execution-price prediction.
What the cost estimate omits
The flat cost rate combines assumptions into a simple sensitivity input. It is not a quote for commissions, spread or market impact. Taxes, borrow charges, financing, settlement and ticket sizes are omitted. The workbench measures a single rebalance and does not annualize it. A real implementation review must use current holdings after market drift, not the previous target weights.
Reproduce and review
Check weights and currencies first, reconcile purchases with sales and cash, then apply the correct rate to each side of a trade. The default is an arithmetic example; it does not represent a managed account. The CSV preserves both sets of weights, portfolio value and the cost convention.
Apply the convention to the synthetic dossier or read the implementation-cost guides.