The short answer
An inventory is a structured description of what the business holds, where it lives, its history and its limitations. It is not the underlying records.
Capture evidence and uncertainty
Record systems, dates, approximate volumes, owners, export methods, exclusions and gaps. Mark anything not yet checked.
Use it to narrow conversations
A provider can respond to a high-level scope before the business considers a sample. Update the inventory as diligence changes what can be included.
What to record before deciding
Keep the written scope, official provider source, unresolved questions and the person responsible for each check. Treat a marketing claim as a claim until it is reflected in the agreement. A directory entry does not approve the transaction or establish your rights to share the records.