@Gustovness: drain code is given in the spell's description, it usually depends upon the force with which you cast the spell. Most of the spells have F/2 + x as drain, where F is the force you cast the spell and x is a constant. In case of a fireball, code is F/2+5, so cast at F2, drain is 6. If F is less than or equal to your Magic, drain is stun. If F is higher than your Magic (maximum 2*Magic), drain is physical damage. So in your case, final drain is 6S. (Meaning, you just took 4S damage from drain.)
A note on calculation: F/2 is rounded down.
Also, a few notes on casting fireball:
- it has a radius of Force meters. You can limit the radius, by not rolling 1 or more dice on your spellcasting test, each withheld die reduces radius by 1 meter.
- As with all spells, you can have a maximum number of hits equal to the Force.
- The targets can try and dodge indirect combat spells as normal ranged attack. (In the drone's case, with Response, -2 dice for the area effect.)