During AS I never actually followed the 1 hour per day per subject rule - instead, I just put in as much time as needed to understand it and write down some clear notes. Most of the time this would be 10-20 minutes, but sometimes hours.
Do as much work as you need to as uberteknik says, but don't overdo it. I can't stress this enough! Spend time relaxing and destressing or you'll find it much harder to grasp things. I can really vouch for this: a lot of people I know stressed themselves for hours on end, whereas I still pulled out 4 A's by just spending a healthy amount of time relaxing and reflecting.
Many people don't realise the impact of a good mental state on your grades. Plan as much as you need to feel organised, and stop there. If you micromanage yourself too much, you end up over-complicating simple problems.
Hope this helps!