Clarify seat assignment billing details in documentation (#62724)

Co-authored-by: Joe Clark <31087804+jc-clark@users.noreply.github.com>

Author: danicaokamoto

content/copilot/reference/copilot-billing/seat-assignment.md

@@ -25,3 +25,4 @@ Users must be assigned a seat to access {% data variables.product.prodname_copil
 * **If a user with an active {% data variables.copilot.copilot_pro_short %}, {% data variables.copilot.copilot_pro_plus_short %}, or {% data variables.copilot.copilot_max_short %} plan is assigned a seat in a {% data variables.copilot.copilot_business_short %} or {% data variables.copilot.copilot_enterprise_short %} plan**, their personal plan is automatically canceled, and a prorated refund for any remaining portion of their personal billing cycle is issued. The user will now use {% data variables.product.prodname_copilot_short %} under the organization's policies.
 * **If a single user receives a seat from multiple organizations within the same enterprise**, the enterprise is only billed once per billing cycle for that unique user. One organization that assigned {% data variables.product.prodname_copilot_short %} to the user is chosen at random each month to be billed for the seat.
 * **If a user is assigned both a  {% data variables.copilot.copilot_business_short %} and a {% data variables.copilot.copilot_enterprise_short %} seat from different organizations within the same enterprise**, only the {% data variables.copilot.copilot_enterprise_short %} seat is billed. The charge is at the {% data variables.copilot.copilot_enterprise_short %} rate from the time the {% data variables.copilot.copilot_enterprise_short %} seat is assigned. The user will have access to the all the features and capabilities available under the {% data variables.copilot.copilot_enterprise_short %} plan.
+* **If a user receives a seat automatically because they were added to a team with {% data variables.product.prodname_copilot_short %} access** (for example, via SCIM or team synchronization), the `copilot.cfb_seat_added` audit log event attributes the action to whoever originally granted {% data variables.product.prodname_copilot_short %} access to that team, not the account that added the new team member. The membership change itself is attributed correctly to the actual actor on the corresponding `team.add_member` or `org.add_member` event. See [AUTOTITLE](/copilot/how-tos/administer-copilot/manage-for-enterprise/review-audit-logs).