the nice answer is a twelve inch plant will double if not triple in sice and get far more bushy. prepare to make room for a flowering plant. if you have a certain strain may stay short, is it young and stringy with spread out nodes/stringy stem, or is it stout and healthy with many nodes tight together. some plants may be small and very thick with folige and thats there strain, almost looks like cabbage, if thats the case you should LST it and have good yeild
28 g. if you have a string bean 17 grams at best with serious care and timing. and have aleast 2 gallon pot if possible to help overall strength and size. (hope that will help you with you question)
oh yeah every node is a growing sight kip that in mind. just a estimit