Confused about my USJ ticket with « ticket price C »

Hi ! I bought tickets recently to go to USJ. I bought them on the official website and I chose the 31st of may for my 1-day studio pass and for my express pass. On the express pass the date is the 31st of may but on the studio pass, it says it’s a ticket price C but the 31st of may is a ticket price B…
I tried to contact the customer support but they’ve not been very helpful thus far…
Thanks in advance !