When we cruised, I made it to FR at about 1:40 on the 1st day and I was the 9th person who signed up on the list. I put an x on every day of the cruise. Although you didn't find out until they called you in the afternoon, I got every evening that I asked for. We also asked for & received one afternoon, that I ended up cancelling for a spa appointment I couldn't get.
However,
We were in a cat 3 cabin. About 3 - 4 months prior to our cruise, making FR reservations was something that the concierge dropped from their services. From reading trip reports , there were some unhappy people who were expecting this kind of help with FR reservations who didn't get this assistance. This is speculation on my part, but it's possible concierge guests were getting all the FR reservations they asked for as a sort of hidden perk. I don't have any explanation other than this as to why I got a spot in FR for all 7 nights of the cruise.
I believe they will try to give you at least 3 nights. And if it's like the cruise I went on you can request as many as you like. Hope this helps!