Question about Reservation Deposit

I've always been afraid to order a dress with a reservation deposit from Dear Celine! I don't want to end up messing up the whole process!
I've been doing some research on how the process works, but I still have a few questions.

Here is the JSK

I understand that ¥300 is the deposit price, but is ¥438 the full price?
Can I pay full price to start out or do I have to pay only the deposit amount?

I really appreciate any help I can get! Thank you, guys!