Clarify auto model selection attribution in Copilot usage metrics (#60374)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: 4 people

content/copilot/reference/copilot-usage-metrics/copilot-usage-metrics.md

@@ -89,7 +89,7 @@ For example schemas of the data returned by the APIs, see [AUTOTITLE](/copilot/r
 | `totals_by_ide` | Breakdown of metrics by IDE used. |
 | `totals_by_feature` | Breakdown of metrics by {% data variables.product.prodname_copilot_short %} feature (e.g., inline chat, chat panel). |
 | `totals_by_language_feature` | Breakdown combining language and feature dimensions. |
-| `totals_by_model_feature` / `totals_by_language_model` | Model-specific breakdowns for chat activity (not completions). |
+| `totals_by_model_feature` / `totals_by_language_model` | Model-specific breakdowns for chat activity (not completions). When {% data variables.copilot.copilot_auto_model_selection_short %} is enabled, activity is attributed to the actual model used rather than appearing as `Auto`. |
 | `last_known_ide_version` / `last_known_plugin_version` | The most recent IDE and {% data variables.copilot.copilot_chat_short %} extension version detected for each user. |
 | `daily_active_cli_users` | Number of unique users in the enterprise or organization who used {% data variables.product.prodname_copilot_short %} via the CLI on a given day. This field is **independent** of IDE active user counts and is **not** included in IDE-based active user definitions. Omitted for enterprises or organizations with no CLI usage on that day. |
 | `totals_by_cli` | Breakdown of CLI-specific metrics for the enterprise or organization on a given day. Independent of IDE metrics—CLI usage is **not** reflected in other fields such as `totals_by_ide` or `totals_by_feature`. Omitted for enterprises or organizations with no CLI usage on that day. See [{% data variables.copilot.copilot_cli_short %} metrics fields](#copilot-cli-metrics-fields-api-only) below. |