I tested those numbers for revenue bookings. As all buckes has 9, it should be possible to book 9 passengers in the lowest fare class.
But I was not able to do that on finnair.com. If I tried to book for 9 pax, either it returned "No flights available". or it returned a price and bucket in the high end. Eg. 1 pax was bookable at 7 000$ while 9 pax was bookable at 11 000$ each.
Not an exhaustive test and maybe somehing else was at play during my test, but seeing J9 C9 D9 R9 I9 in EF may or may not indicate they actually have 9 seats free.