Because its wasted spark, it doesnt just fire once per cycle on each cylinder like a normal coil set up,
wasted spark gets it name from firing twice, as it fires cylinder 1 and 4, then 2 and 3 in pairs, it will fire once as normal on the compression stroke, but also once on the exhaust stroke which is wasted.

(IE, if cylinder one is one the compression stroke and gets spark, the coil is also firing cylinder 4 which is on its exhaust stroke).

The coil pack is basicly two coils in one unit.

If you run into rev counter issues, you can also make a diode pack to run from both sides of the coil to feed the rev counter.