[Editorial] SubAccountID: convert normative statements into bullet po…

…ints (#632)

This PR is in alignment with Issue #606

specification/columns/subaccountid.md

@@ -2,7 +2,11 @@
 
 A Sub Account ID is a provider-assigned identifier assigned to a [*sub account*](#glossary:sub-account). Sub Account ID is commonly used for scenarios like grouping based on organizational constructs, access management needs, and cost allocation strategies.
 
-The SubAccountId column MUST be present in a [*FOCUS dataset*](#glossary:FOCUS-dataset) when the provider supports a *sub account* construct. This column MUST be of type String. If a charge does not apply to a *sub account*, the SubAccountId column MUST be null.
+The SubAccountId column adheres to the following requirements:
+
+* The SubAccountId column MUST be present in a [*FOCUS dataset*](#glossary:FOCUS-dataset) when the provider supports a *sub account* construct.
+* This column MUST be of type String.
+* If a charge does not apply to a *sub account*, the SubAccountId column MUST be null.
 
 See [Appendix: Grouping constructs for resources or services](#groupingconstructsforresourcesorservices) for details and examples of the different grouping constructs supported by FOCUS.