Canadian sponsorship visa: refund received before acknowledgment of receipt?

Hi, I have applied for a canadian sponsorship visa with my partner from outside Canada. We sent out application along with a bank draft for the fees : 75 CAD for Sponsorship application 490 CAD for Right of Permanent Residence Fee and 475 CAD for Principal applicant. Today I received a bank draft for 475 CAD from the canadian government but with no letter of explanation. The only other writing on the invoice was refund: incorrect fees 475 CAD. Does this mean our application has been denied at the sponsor processing stage? Any help appreciated, it's pretty tough being in the dark. Thanks in advance.