Update platform.md

Signed-off-by: Jesse Brown <jabrown85@gmail.com>

Co-authored-by: Emily Casey <emilykimballcasey@gmail.com>

platform.md

@@ -311,9 +311,10 @@ Usage:
 | `<tag>...`        |                       |                          | Additional tag to apply to exported image
 | `<uid>`           | `CNB_USER_ID`         |                          | UID of the stack `User`
 
-- **If** `<daemon>` is `false`, `<image>` MUST be a valid image reference
-- **If** `<daemon>` is `true`, `<image>` MUST be either a valid image reference or an imageID
+-`<image>` MUST be a valid image reference
 - **If** the platform provides one or more `<tag>` inputs, each `<tag>` MUST be a valid image reference.
+- **If** `<daemon>` is `false`, and `<previous-image>`, if provided,  MUST be a valid image reference
+- **If** `<daemon>` is `true`, `<previous-image>`, if provided, MUST be either a valid image reference or an imageID
 - **If** `<run-image>` is not provided by the platform the lifecycle MUST [resolve](#run-image-resolution) the run image from the contents of `stack` or fail if `stack` does not contain a valid run image.
 - The lifecycle MUST accept valid references to non-existent images without error.
 - The lifecycle MUST fail if the stack ID of the `<run-image>` does not match `<stack-id>`