Both Rows and Size columns from the Objects browser are initially just estimates collected from your database on the first import. Some platforms give us the exact row count, others (like PostgreSQL) provide an just approximate number. For 1-2 rows in the table, collected Rows could be 0.
Rows value is never automatically updated when rows are added or removed. But, whenever you need a refresh, you can select one or more tables, and execute the contextual Update Row Count command, as in the image below. A SELECT COUNT(*) will be executed right away for each selected table, and Row value updated. Be careful with this command, because the query may be slow on very big tables.