ref: mention config reads from all config files combined (#3359)

per #1368 (comment)

content/docs/command-reference/config.md

@@ -22,9 +22,9 @@ takes a config option `name` (a config section and a key, separated by a dot)
 and its `value` (any valid alpha-numeric string generally).
 
 When reading config options (no `value` is given or `--list` is used), the
-values are read from the system, global, project, and local config files (in
-that order). The `--system`, `--global`, `--project`, and `--local` options can
-be used to read from that configuration only.
+values are read from a combined set of values from the system, global, project,
+and local config files (in that order). The `--system`, `--global`, `--project`,
+and `--local` options can be used to read from that configuration only.
 
 When writing (a `value` is given or `--unset` is used), the new value is written
 to the project-level config file by default (`.dvc/config`). Options `--system`,