I don't think it matters, personally I made mine by saying the date in full (ie "wednesday the 5th may" or whatever), then the restaurant ("Le Cellier, in Epcot" - just to avoid any accent problems!!), then the time preferred.
I think I remember hearing that their computers are set up for them to click the restaurant first, so it might speed things up slightly by asking for the restaurant first, but it won't be that much quicker I don't think