How can I visualize dbms_olap.estimate_summary_size output? I run the following code under sqlplus:

1 DECLARE
2 num_rows number;
3 num_bytes number;
4 BEGIN
5 --dbms_olap.estimate_summary_size('pippo','select * from cat',num_rows,num_bytes);
6 dbms_output.put(num_rows);
7 --dbms_output.new_line;
8 --dbms_output.put(num_bytes);
9 dbms_output.new_line;
10* end;

but I had only 'PL/SQL procedure successfully completed'.
How can I visualize num_rows? Thanks

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