If I'm reading it correctly, the shifts work like this:
- Calculate total power of the spontaneous magic: 2 * 2 * 5 = 20
- Compare power level to your skills: Power = 20, your skills = 8, you fall short, so you have to calculate the shifts.
- Compute the amount of power you are short by independently subtracting the base and intent skill level from the power required, then adding them together.
- Power - Intent: 20 - 4 = 16
- Power - Base = 20 - 4 = 16
- 16 + 16 = 32
- Divide the total by 5: 32 / 5 = 6.4. Apparently it rounds up. So you get 7 shifts. Ouch.
