Document Intelligence F0: ProcessedPages metric missing, how to read monthly pages used, and what Delete Analyze Result guarantees

We use Azure AI Document Intelligence (F0, Japan East, REST API 2024-11-30, prebuilt-layout).

We need to monitor the 500-page monthly free allowance accurately before submitting documents.

Observed behavior:

• Azure Monitor exposes only eight metrics: BlockedCalls, ClientErrors, Ratelimit, ServerErrors, SuccessfulCalls, SuccessRate, TotalCalls, TotalErrors.
• ProcessedPages is unavailable.
• The Portal's Processed Pages chart shows a data retrieval error.
• The resource Usage API returns FormRecognizer.Transactions (Count, limit 500), but its unit semantics are unclear.

Questions:

1. Why is ProcessedPages unavailable on this F0 resource?
2. Does FormRecognizer.Transactions count pages, documents, or requests?
3. Which official API provides the monthly processed-page count?
4. Does exhausting the F0 allowance only reject requests, or can additional charges occur?
5. Do failed or cancelled analyses count toward the allowance?
6. Does Document Intelligence Studio usage count toward the same allowance?
7. If Operation-Location is lost, how long are results retained, and can they be deleted without it?
8. Does Delete Analyze Result HTTP 204 indicate physical deletion or only that deletion was flagged? Would a later GET return 404?

We need an authoritative, supported way to track F0 usage without risking paid overages.

Thank you.