I also need to fill this form but I really don't know what Visa office processes my application. I wrote an email to
CPC-CTD-Ottawa@cic.gc.ca and currently waiting for the reply.
Kyiv Visa Office said that I can find this information in MyCIC AOR letter but there is no such information in it.
UPDATE: I found info, that it is normal to write IRCC in office name and ONLINE in office address.