FICTIONAL API COST LEDGER — v1
Period: one 30-day project period; one currency; postpaid example.
This is a usage-period COST FORECAST, not payments due in the period. API payment can fall later; cash flow requires a separate schedule using actual due dates.
Before real use: fill actual start/end/timezone, meter scope, report URL/reference and cutoff timestamp. No credentials.
Rate: $2 per 1,000 billable units; unchanged in this example.
Fixed charges in this period: Tool A $18 + Tool B $12 = $30.

SNAPSHOT A — reported through day 10 (retained history)
Cumulative units: 4,500; cumulative reported API: $9.
Remaining scenario after cutoff: 6,000–12,000 units = $12–$24.
Full-period API forecast: $9 + $12–$24 = $21–$33.
Combined forecast: $30 + $21–$33 = $51–$63.

SNAPSHOT B — reported through day 20 (CURRENT)
Cumulative units: 10,500; cumulative reported API: $21.
REPLACE the earlier $9 with $21; do not add both observations.
Remaining scenario after cutoff: 2,000–4,000 units = $4–$8.
Full-period API forecast: $21 + $4–$8 = $25–$29.
Combined forecast: $30 + $25–$29 = $55–$59.
Reported change: $21 − $9 = $12, already included in the current cumulative $21.

Assumptions: scenarios are chosen estimates, not guaranteed bounds. Report may lag or be corrected. No tax or unverified credit/discount/adjustment included; those items remain unresolved, not zero.
Next review: confirm report cutoff and scope; replace cumulative observation; re-estimate only remaining usage; revise separately for verified adjustments.
At close: reconcile with final billing record. API review dates are not fixed renewal charges.