photoshop CS6 stroke use 2 path ?

Hi

I draw a curves path in  photoshop using 2 direction line and 2 anchor point .

when i add a stroke  i was thinking the stroke will follow the b path line see in 1  but stroke is follow a and b path .

i was expected to have 3 case  . Is it the default behaviour ?

Howto  have stroke only on the b path not the a path ?

if i create a font type letter u  i don't want the line a  !!!

regard's