My SQL(v - 5.0.12) auto-increment randomly incrementing values in the range of 1-6

I am working on a prestashop(1.6.1.7) project. set the autoincrement and autoincrement offset variables to 1. Truncated the tables . While inserting it randomly set's the id_customer which is the primary key and autoincrement field in customer table sometimes it starts with 6 sometime 1.

id_customer field also has an index

Also tried dropping the id_customer field and recreating it.