Not sure what you mean.

Gleis 7 combined with 1-year 1/2: Fr249
Gleis 7 if you already have a 1/2: Fr99
1-year Halbtax: Fr150
Fr150+99 = Fr249, so there's no financial gain to be had.

Here's where the Gleis 7 is valid (after 7pm only, natch):
http://www.gleis7.ch/_upload/content...ichtskarte.pdf

Note that it's only valid on local transport (buses, trams, etc) in towns marked with a dot-inside-a-circle.