They're describing "+=" as a single operator, not a combination. "-=" is a different single operator, as is "/=" and and all the others. The first character a

They're describing "+=" as a single operator, not a combination. "-=" is a different single operator, as is "/=" and and all the others. The first character and the "=" are inseparable, they just have all the combinations defined as independent operators. They're comparing it to a language where the first part (which can be multiple characters!) is actually separate from "=".