It's saying "Duplication something-something" For 30, What am I doing wrong?

If it's duplicate label, then it's because you have 2 @HPBARS. You want to add gosub before all labels on lines 24-26.

What should I do for 30 though?

30 is fine assuming you have a return command somewhere. @MAIN looks ok too, although you would be much better off with a while/wend or repeat/until loop, but then I would replace your gosub calls with functions/subroutines too. Anyway, gosub @label to jump to a line of code. return to go back where you came from, and @label to define a point to jump to.

Yeah, line 30 is fine. That's where one of your gosubs go. GOSUB @HPBAR means it's going to go to the label @HPBAR, and somewhere on a line below line 30 there should should be a RETURN.

You're also going to need PRINT for each line of the box. And they'll need parentheses as well, the second line doesn't have any. If done right, each line will be gray unless it's a variable. Hope that helps