diff --git a/admin-guide/container.md b/admin-guide/container.md
index bc9b0af1..e180b2c4 100644
--- a/admin-guide/container.md
+++ b/admin-guide/container.md
@@ -30,7 +30,7 @@ To be able to run rootless containers with podman you need to define a subuid/su
 
 To be able to have these ids consistent PSI wide there is a small central database/API to register and lookup such IDs.
 
-The API endpoint is `https://sysdb.psi.ch/subid/v1/config` and allows for one or more `user` parameters. It will then return the line(s) you need to add to `/etc/subuid` and `/etc/subgid`.
+The API endpoint is `https://sysdb.psi.ch/subid/v1/config` and allows for one or more `user` parameters. Valid are numeric user ids (uid) or any username listed in our AD. It will then return the line(s) you need to add to `/etc/subuid` and `/etc/subgid`.
 
 Note that the ID is now reserved for 2 years. With every lookup with the API the reservation gets renewed. After it timed out the ID range will be freed and will be used by someone else.