:salam2:, the transliteration was correct when it ends with an '-i'. This is because the letter 'yaa' at the end indicates 'me' in arabic. When reciters say the prayer in witr, they are doing the dua for the whole congregation and so it changes to '-na' which is 'us'. If you are reciting the du'a to yourself, then keep it to the '-i' ending. If in congregation, change it to '-na'