It can be as many servings as you want it to be :) What I do for ones like that, is I start with a number and see how many calories it is. Like for a casserole in a large pan, I do 6 servings. If it's too much, I switch it to 8, or whatever the next number would be in the sequence. And, vice versa if it's smaller than I thought it would be. I do that until I get it to a calorie number I'm comfortable with.
For a bread loaf pan, assuming it's a 9x5x3 pan, 8 servings is usually a good number. If it's a smaller loaf pan, then maybe 6. But, like I said, it can be whatever you want it to be.