Assuming that the answer is the same as in Twilight Canon, here's why this works(if you have not read the books and do not want to spoil yourself, do not decipher, obviously):

Va Gjvyvtug Pnaba, Ryfcrgu(be engure, Erarfzrr be jungrire gur cbxrzba vf pnyyrq) cbffrff na 'vairefr' cbjre gb ure cneragf. Vr. juvyr Rqjneq pna ernq zvaqf, fur pna fraq gubhtugf. Naq juvyr Oryyn vf fuvryqrq, fur pna crargengr fuvryqf.