The Offspec score works with Dual Talent Specializations. It will display the statscore for whatever spec is not currently active.

Setup is simple.

1. Switch to your Primary spec.
2. Type /StatScore
3. Select the profile that best matches your spec
4. Press Ok
5. Switch to your Secondary spec.
6. Repeat Steps 2-4

Now StatScore knows what profile to load for each specialization, and will automatically swich profiles when you switch your spec. Your offspec will be the specialization that is 'off' or inactive.