In my experience, years of professional experience != Seniority

You could have been for 18years in a company where you were the senior just because you were the only one who knew how the old monolite work. You could have been for 18years in a company without knowing more than what you were just doing. This just to say that the seniority it's not something you obtain with your years but with the experiences and situations you find yourself in and especially what do you learn from them.