Indentation means the number of spaces, to make the code valid. So if you start with using tabs you need to go with all tabs. So that makes no tabs for *choice then one tab for #option then 2 tabs for *finish or *goto command. The same goes for spaces. So it will either look like this
*choice
#option
*finish
Or this
*choice
#option
*finish
Or whatever spaces/tabs you want. (Remember! Spaces or tabs.)
What im trying to say is you need pre-determined indentation type + indentation level.
Indentation type means you wheter use space or tab to indent a line
Indentation level means whether you use one space/tab or two space/tab to indent a line.
So this will be wrong;
*choice
#choice1.
*finish
#choice2.
*finish
Or even if your indentation level is true, if your indentation type is not the same, it will give errors such as the one you asked in this thread.