The type of spell determines the range

In your instance, you're casting a fireball, an indirect spell that doesn't exactly require line of site to the target. Pg. 283 says of Indirect spells:

So you don't really need to be able to see the target — you can cast these spells blindfolded or with artificial image enhancement — as long as you've got a clear line of fire.

An example of something different would be Detection spells (pg. 285):

The standard range of the sense a Detection spell grants is the spell's Force x caster's Magic in meters as a radius from the target of the spell. Extended-range detection spells have a Force x Magic x 10 meter range.

So, technically, if you're casting Fireball you could use digital binoculars if you wanted. Essentially follow the directions you listed, then read the introduction for the section that holds the spell you're casting.