Step 3 of 18 of the SQL tutorial. ORDER BY sorts the whole result, and LIMIT takes the front of it — in that order, so the ten most widely supplied come back, not ten arbitrary rows sorted. Mango spells the same pair sort and limit. Its sort takes a direction per field, and every field must run the same way. Note the selector {"nbSuppliers": {"$gt": 0}}: a real CouchDB refuses to sort on a field the selector does not mention, because the sort needs an index.
It opens on the query SELECT preferred_name, formula, nb_suppliers FROM compounds ORDER BY nb_suppliers DESC LIMIT 10, which you can run and change in place.
Ask the same question of a chemical dataset in SQL and in Mango and compare the two answers. The database is a SQLite file your browser downloads once and queries locally, so nothing you write ever leaves your machine — which is also why the tool needs JavaScript.