Clarify restore

Signed-off-by: Natalie Arellano <[email protected]>

Author: Natalie Arellano

content/docs/reference/spec/migration/buildpack-api-0.6-0.7.md

@@ -27,7 +27,9 @@ Valid `<ext>` extensions are as follows:
  | `application/spdx+json`          | `spdx.json`
  | `application/vnd.syft+json`      | `syft.json`
 
-SBOM files for launch will be included in the application image if the platform api supports it; SBOM files for build may be saved off by the platform prior to the build container exiting. Layer-associated SBOM files will be cached and restored to the buildpack layers directory on re-builds of the same image (much like the `<layers>/<layer>.toml` metadata file).
+SBOM files for launch will be included in the application image if the platform api supports it; SBOM files for build may be saved off by the platform prior to the build container exiting.
+
+Layer-associated SBOM files will be cached and restored to the buildpack layers directory on re-builds of the same image (much like the `<layers>/<layer>.toml` metadata file). `<layers>/launch.sbom.<ext>` and `<layers>/build.sbom.<ext>` must be re-created on each build.
 
 The `[bom]` tables in launch.toml and build.toml are no longer supported.