diff --git a/docs/METRIC-CATALOGUE.md b/docs/METRIC-CATALOGUE.md
index 6898f7f..b05feca 100644
--- a/docs/METRIC-CATALOGUE.md
+++ b/docs/METRIC-CATALOGUE.md
@@ -1,11 +1,20 @@
 # Analytics Metric Catalogue
 
-- Status: Draft — listed definitions approved
+- Status: Approved specification — implementation not yet authorized
 - Version: 0.4.0
 - Last updated: 2026-08-20
 
 Every merchant-facing number identifies its grain, formula, source fields, filters, Tehran-local period, unit, missing-data behavior, trace path, and definition version.
 
+## Physical source mapping
+
+- Session-grain metrics read `payment_sessions`, scoped by `merchant_id` and the approved half-open `created_at` period.
+- Attempt-grain diagnostics and timings join `payment_attempts.payment_session_id` to the already merchant-scoped session set.
+- Money uses `payment_sessions.amount_rial` and `payment_sessions.fee_amount_rial` exactly once per session.
+- Terminal filters join the session's `terminal_id`; peer cohorts join the merchant's `category_id` and exclude the active merchant.
+- The sole completed `import_runs` row identifies the immutable MVP dataset snapshot included in cache/result metadata.
+- `calendar_dates` defines Saturday–Friday weeks, Jalali months, and Persian seasons; no holiday dimension exists.
+
 ## Bank-paid sessions
 
 - Canonical id: `bank_paid_sessions`
@@ -49,7 +58,7 @@ Every merchant-facing number identifies its grain, formula, source fields, filte
 ## Paid volume
 
 - Canonical id: `bank_paid_amount_rial`
-- Formula: sum session `amount` once where `session_status IN ('Paid', 'Verified')`
+- Formula: sum session `amount_rial` once where `session_status IN ('Paid', 'Verified')`
 - Unit: Rial
 - Subsets: `verified_amount_rial` uses `Verified`; `unverified_paid_amount_rial` uses `Paid`