I've booked many Aeroflot Comfort Class flights the last couple years. When you click on the flight you want, it will show you 2 options for economy, and 2 options for Comfort......the first in each cabin is more restrictive than the second option, which of course is a higher price.
As long as you book ANY Comfort Class fare, you should get 100% RDM and MQM's with Delta. Comfort class often is only $100-$200 more each way than the normal Economy class...... so better seats and 100% miles instead of 25% (or possibly 50%) RDM/MQM's. And you can book one ways for the same price or just a small upcharge.
"Comfort Class/A" should be all that is needed to get the proper miles, imho. A proper receipt would be nice, perhaps, but I guess that is what you mean by "ticket" that you sent them?
Did you buy from aeroflot.com or aeroflot.ru ? Orbitz? I guess not DL.Com, as I have never seen an SU option on dl.com.