See the number in bold at the end of the line in export_descr_unit.txt

type generic siege 3span
dictionary generic_siege_3span ; Triaspanai Katapeltai
category siege
class missile
voice_type General_1
soldier greek_artillery_crew, 24, 8, 0.85
engine scorpion
attributes sea_faring
formation 1.5, 1.5, 3, 3, 3, square
stat_health 1, 0
stat_pri 4, 2, no, 0, 0, melee, simple, piercing, knife, 0 ,0.1
stat_pri_attr no
stat_sec 12, 2, scorpion, 350, 30, siege_missile, blade, piercing, none, 25 ,1
stat_sec_attr ap, bp
stat_pri_armour 0, 8, 2, flesh
stat_sec_armour 0, 0, flesh
stat_heat 0
stat_ground 0, 0, 0, 0
stat_mental 4, normal, untrained
stat_charge_dist 30
stat_fire_delay 0
stat_food 60, 300
stat_cost 1, 5000, 1900, 30, 40, 5000
ownership thrace, greek_cities, macedon, romans_julii, numidia, egypt, spain, romans_brutii, seleucid, slave, carthage

That number affects lethality more than virtually anything else. The higher it is, the faster your units swing with their weapons, increasing the probability of a killing blow.