How to count a joined foreign table?

The doc only shows how to count a table without joined foreign tables:
https://supabase.com/docs/guides/database/tables#joining-tables-with-foreign-keys

Using the example below which gets messages from a certain user:

const { data, error } = await supabase
  .from('messages')
  .select('*, users!inner(*)');

const { data, error } = await supabase
  .from('messages')
  .select('*, users!inner(*)');

How to count the joined

users

users

table?

Creating and using Postgres tables.