compare size values between original table and copied one

Original query:

my_db=>  select oid::regclass, pg_relation_size(oid), pg_table_size(oid), pg_total_relation_size(oid) from pg_class WHERE oid = 'molecule'::regclass;
   oid    | pg_relation_size | pg_table_size | pg_total_relation_size 
----------+------------------+---------------+------------------------
 molecule |       3429744640 |    3430670336 |            25694060544


my_db=>  select oid::regclass, pg_relation_size(oid), pg_table_size(oid), pg_total_relation_size(oid) from pg_class WHERE oid = 'molecule_bis'::regclass;
     oid      | pg_relation_size | pg_table_size | pg_total_relation_size 
--------------+------------------+---------------+------------------------
 molecule_bis |       3404955648 |    3404963840 |             3404963840