Correct.
The x3 was specifically a modifier set to any penalties, not bonuses(boni?).
So anything that was “bad”(less than full casting rounds based off of spell Class-I, II, III, IV; using less hands/voice; wearing restrictive materials/armours) is counteracted by “good” boni(taking longer to cast, extra hands; louder voice).
If one fumbles the SCSM, like your Mage, you then triple *just* the negative mods and add them to a d% looking at the Spell Failure chart that references whether it was an Attack Spell or Non-Attack Spell.
No previous positive boni are used to alter this roll, only the negative ones.