Clarify meaning of "root-level fields" in the documentation. (#11143)
diff --git a/docs/ingestion/index.md b/docs/ingestion/index.md
index ccc9f0b..a8bae6b 100644
--- a/docs/ingestion/index.md
+++ b/docs/ingestion/index.md
@@ -489,12 +489,13 @@
Schemaless interpretation occurs when both `dimensions` and `spatialDimensions` are empty or null. In this case, the set of dimensions is determined in the following way:
-1. First, start from the set of all input fields from the [`inputFormat`](./data-formats.md) (or the [`flattenSpec`](./data-formats.md#flattenspec), if one is being used).
-2. Any field listed in `dimensionExclusions` is excluded.
-3. The field listed as `column` in the [`timestampSpec`](#timestampspec) is excluded.
-4. Any field used as an input to an aggregator from the [metricsSpec](#metricsspec) is excluded.
-5. Any field with the same name as an aggregator from the [metricsSpec](#metricsspec) is excluded.
-6. All other fields are ingested as `string` typed dimensions with the [default settings](#dimension-objects).
+1. First, start from the set of all root-level fields from the input record, as determined by the [`inputFormat`](./data-formats.md). "Root-level" includes all fields at the top level of a data structure, but does not included fields nested within maps or lists. To extract these, you must use a [`flattenSpec`](./data-formats.md#flattenspec). All fields of non-nested data formats, such as CSV and delimited text, are considered root-level.
+2. If a [`flattenSpec`](./data-formats.md#flattenspec) is being used, the set of root-level fields includes any fields generated by the flattenSpec. The useFieldDiscovery parameter determines whether the original root-level fields will be retained or discarded.
+3. Any field listed in `dimensionExclusions` is excluded.
+4. The field listed as `column` in the [`timestampSpec`](#timestampspec) is excluded.
+5. Any field used as an input to an aggregator from the [metricsSpec](#metricsspec) is excluded.
+6. Any field with the same name as an aggregator from the [metricsSpec](#metricsspec) is excluded.
+7. All other fields are ingested as `string` typed dimensions with the [default settings](#dimension-objects).
> Note: Fields generated by a [`transformSpec`](#transformspec) are not currently considered candidates for
> schemaless dimension interpretation.
