(2E)-geranyl diphosphate + S-adenosyl-L-methionine = (E)-2-methylgeranyl diphosphate + S-adenosyl-L-homocysteine + H(+)
(2e)-geranyl diphosphate + s-adenosyl-l-methionine = (e)-2-methylgeranyl diphosphate + s-adenosyl-l-homocysteine + h(+)