Phpmyadmin Table Checks Warnings

I used Phpmyadmin Table Checks / Repair functions and see warnings below; What is does mean?

Problems with the indexes of the table oc_t_category
The index i_position and i_position_2 look equal and it may be possible to delete one of them.
The index fk_i_parent_id and fk_i_parent_id_2 look equal and it may be possible to delete one of them.
Problems with indexes of table oc_t_city
The index fk_i_region_id and fk_i_region_id_2 look equal, and it may be possible to delete one of them.
Problems with the indexes of the table oc_t_city_area
The index fk_i_city_id and fk_i_city_id_2 look equal and one of them may be deleted.
Problems with the indexes of the table oc_t_item
The index fk_c_currency_code and fk_c_currency_code_2 look equal and one of them may be deleted.
Index fk_i_category_id and fk_i_category_id_2 look equal and one of them may be deleted.
The index fk_i_user_id and fk_i_user_id_2 look equal and one of them may be deleted.
Problems with the indexes of the table oc_t_item_comment
The index fk_i_item_id and fk_i_item_id_2 look equal and it may be possible to delete one of them.
Problems with indexes of table oc_t_item_resource
The index fk_i_item_id and fk_i_item_id_2 look equal and it may be possible to delete one of them.
Problems with the indexes of the table oc_t_item_stats
The index dt_date and dt_date_fk_i_item_id appear equal, and it may be possible to delete one of them.
The index dt_date and dt_date_2 look equal and it may be possible to delete one of them.
Problems with the indexes of the table oc_t_keywords
The index fk_i_city_id and fk_i_city_id_2 look equal and it may be possible to delete one of them.
Index fk_i_category_id and fk_i_category_id_2 look equal and one of them may be deleted.
Problems with the indexes of the table oc_t_plugin_category
Index fk_i_category_id and fk_i_category_id_2 look equal and one of them may be deleted.
Problems with indexes of table oc_t_region
The index fk_c_country_code and fk_c_country_code_2 look equal, and it may be possible to delete one of them.