Follow the entire task.
Current effort is handling plus review. Proposed effort includes the work still done by people, plus a lower and higher review estimate. Only the share of cases covered by the proposed workflow changes; the rest keep their current effort.
Time is capacity.
Released hours are multiplied by your reusable share and loaded hourly cost. That represents a value for redeployable capacity. It does not automatically reduce payroll, create revenue or become cash. If the change adds work, that additional effort is counted in full.
Let the costs stay visible.
Monthly operating cost is subtracted from capacity value every month, and implementation cost is deducted at the start. Cost coverage means the accumulated modelled capacity value has covered the entered costs. It is not a cash payback forecast.
Test the assumptions.
The model holds volume, coverage, rates and effort constant from month one. It excludes rollout delays, ramp-up, inflation, financing, taxes, discounted cash flows, revenue effects and costs you have not entered. Use representative completed cases to challenge the estimates, then revisit the calculation.