IF weapon specifically has in description that it changes some skills so that new variant does magic type of damage.
Checking now due ranger being example, ranger here in game has all it's attacking actions (Piercing shot,Suppressing fire,Point-blank shot, etc) causing physical, except for Signalling flare which is magical.
Open character screen again and hover mouse over skill to get description. That is where is written base damage, which is then modified by stats, as well by various buffs on characters.
So ranger starter skills:
Piercing shot:
5-7 physical, 5% crit, available if character in 2 left most spaces, can attack all enemies except left most one, ignores Guard buff on enemy and remove whole stack
Suppressing fire:
2-4 phys, 5%, crit, must be in any position but right most, attacks all enemies at once
Signalling flare:
2-3 magic, be in any place but right most, can attack any enemy, ignores defense token while removing dodging buff and invigorating one (resistance to status effects), adds vulnerability (enemy gets more damage)
Weapons don't have, say, 2-6 or 1-4 damage listed.
Instead their stats are more like, or example, +10% or 20% bonus to damage and/or any other modifiers, like changing certain skills or otherwise affecting stats.
Ignore background in Dungeon and dragons tabletop.
A bit of familiarity with video game Darkest dungeon or any of various games imitating it's combat mechanics (like this one) helps bit more.
