thanks
更新1:
But I have checked a few dictionaries, and the phonetic symbol for those words is really 'tn', no vowels between 't', and 'n'.
更新2:
Or some dictionaries show a smaller 'inverted e' at the top right corner of 't'. Are there any differences between 'tn' / 't(smaller inverted e)n' and 't(inverted e)n'?