@skuben:
Let' say I am a Mage with Magic (6), Spellcasting/Combat Spells (6). I know Lightning Bolt which has a Drain Value of (Force-3). I am facing an opponent who I really need to put down, but want to do it in a way that doesn't do me any lasting damage. I also have a handful of reagents.
I can choose to cast that Lightning Bolt at a maximum of Force 12 due to my Magic (6) as you can cast a spell at a Force up to twice your Magic rating. I have 14 dce to roll on the spellcasting test between my Attributes, Skills, and Specialization. Let's say I get lucky and roll 7 hits. My opponent rolls to dodge the spell and gets 3 hits, reducing my net hits to 4 hits and setting the damage from the spell at 16P (Force 12 + 4 net hits). BUT, because I didn't use reagents to set a limit, I now must resist against 9P drain (physical because the number of hits (7) is greater than my Magic (6) rating).
If I were to use 6 reagents to set the limit at 6 and using all of the other previous rolls, the spell would go off with 6 hits (even though 7 were rolled due to the reagent limit in place), still hit my opponent with 3 net hits (6-3), do 15P (Force 12+3 net hits) damage, but I would be facing 9S damage instead of 9P damage as the number of hits equals my Magic (6) rating due to the imposition of the limit from the reagents.
Someone correct me if I got anything wrong.