I just got a new viola case?

I just recently ordered a new viola case of of amazon and just got it today thing is it said it was for 15-17 and my viola is a 16 1/2 and get this i get it and it doesn't fit i swear i checked four times on the website to see if it was the right size and it doesn't fit what do i do on the website it says its adjustable so how does it adjust does it at all it's a seventy dollar prelude viola case please help me please