I think the value of the auto_increment column is not decreased automatically; you need to manually run queries to reset the value to the current maximum value.
You can run the following SQLs to reset the value.
1. Find the value for the auto_increment column you will reset to.
SELECT MAX( column_name )+1 FROM table_name;
2. Reset the value of the auto_increment column. Let's say the output of the above query is 100.
ALTER TABLE table_name AUTO_INCREMENT = 100