The new system has been good at letting you know what it is when you book. I think it will be lunch, but I don't know for sure.
I remember last year booking what I thought was breakfast and then found out it was lunch, I was able to get an earlier ADR.
When you look it up does it say Donald's Safari Breakfast or Tusker House? If you can't find anything saying breakfast or Donald's Safari Breakfast then I would guess you have a lunch reservation.