Assign interval multiple value into characteristic

Dear Guru,

hello, i'm new on Variant Configuration and need your input.

I have dependency characteristic and I want to assign multiple value as a precondition. In the editor I wrote below syntax :

     $set_default($self, tpreast, in(6 - 11))

I want to put multiple value to characteristic tpreast from 6 to 11. but the above syntax generated error message :

     Reference to object $root, $parent, or $self required

Please let me know the correct syntax for above requirement. Appreciate your help.

Thank you,

Budi