A Character hac a Parma of 5 and a Herbam of 10 what will his resistance be
- Parma x 5 (25) plus Herbam (10) for a 35..
or
- Parma x 5 (25) plus Herbam Bonus 10 / 5 (2) for a 27
Official rulling please
The first one, 5 X Parma score plus the full Form score.
In a related note, you get to add 1/5th of your Form score to soak or other resistances that involve it. So in this example, even if the spell penetrated, you'd still get +2 on your soak.
option one; 35.
Left hand column on page 85, second paragraph under magic resistance, "Hermetic magi have a base magic resistance equal to their score in the form most..."
Then also in this column in the first paragrapgh under the heading "Parma Magica"; "The Parma magica... adds to the resistance arrising from a maga's form scores" (emphasis mine)
Notice on page 77 that the form bonus is "Form score / 5 (rounded up)" (once again, the underlines are mine).
It is difficult to believe that if the author and editors had meant "Form Bonus" that they would have used the term "form score".
Editions 2, 3, and 4 have used your option #1 as well and provided explicit examples.
Which is what I believe the first full paragraph in the midle column of page 77 is referring to with "...helps you resist spells of that type..." in the sentence imediately before the book talks about form bonuses (yes, it could have been written more clearly).