my boss, the owner of the company, had me explain my job to him at least 3 times during my time there. He was the one that hired me and still didn't know exact

my boss, the owner of the company, had me explain my job to him at least 3 times during my time there. He was the one that hired me and still didn't know exactly what I did. It was extremely frustrating when he asking me to do graphic design work and he didn't understand why it wasn't part of my job (I was hired as a developer, I wrote their entire e-commerce system which ran their business for 4 years).