I do not know the school in Tuen Mun. I think you can be admitted to the Band one school. so go to the school you like & try as you have two chances.
Then, put them as your first and second choice in the computerised control list, then put the next bading school in the form and you should request your teachers to help you to fill in the form properly.
Dont worry, Try the school you like ( 2 chances) so do not miss the chances to go to the school yuo like.