I picked nine fruits because the recipe said eight large and although mine are huge, the fruit inside is considerably smaller. I prepared them using my favorite method, then chopped them finely.
I didn't want to get my canner out for just three little jars, so after ladeling the jam into the jars (three, not four the recipe promised me--maybe I should have gotten ten or twelve grapefruits), I washed the pot out, got the water hot, put the three little jars in, then brought it all up to a boil.
Oh, and I've already heard the tops on all three jars click. They are sealed!