If I brew a potion, does it brew of a strength relative to my level, or to the innate level of the spell?

Related, I keep seeing a little number in parentheses in spell descriptions - is that the innate level?

Thanks.

Moved to appropriate forum.

You brew/craft according to innate spell level. The number in the paranthesis is the spell's caster level.

So a bulls strength which is innate level 3, but brewed by a level 9 caster will last for 9 hours (as it's 1hr/level) instead of 3 hours?

No, that would mean you'd be brewing/crafting according to level. Innate level is the innate level in the spell description. Brewed and crafted spells are always as weak as possible, unless we have exceptions for certain spells which I wouldn't know about.

There are a few potions which brew at levels higher than the class level of the caster who made them, presumably because they would be useless otherwise. There are also a few EfU-specific potions which have extended durations.

On the whole, the system is pretty well-balanced.