I am attempting a Tasmanian recipe for blood orange, pomegranate and cardamom jelly. The quantities are all is Tasmanian (e.g. milleliters and grams). It only took math skills to solve that challenge. The greater one was when it called for "caster" sugar. I think this means something roughly the equivalent of powdered sugar or confectioner's sugar, but who knows? And why call it caster?