The mod adds 45 and 60 arrows/bolts versions of various arrow/bolt quiver that the mod RBM offers. This mod exists because I feel stupid being limited to mere 30 arrows, so now there are 45 and 60 variations of the default vanilla 30 arrows/bolts.

If you want to make another variation of a quiver with your stack amount, like 90, 120 or 3005, you can do something like the following in this example:

<Item id="GRE_heavy_steppe_arrows_45" name="45 Greased Needle Bodkin Arrows 60 grams" body_name="bo_capsule_arrow" mesh="arrow_bl_d" weight="0.06"  appearance="1" Type="Arrows" item_holsters="quiver_back_lower:quiver_back_lower_2" holster_position_shift="0.0,0.0,-0.0" is_merchandise="true" holster_body_name="bo_axe_short" holster_mesh="arrow_bl_f_quiver" holster_mesh_with_weapon="arrow_bl_f_quiver" flying_mesh="arrow_bl_flying">
        <ItemComponent>
            <Weapon weapon_class="Arrow" modifier_group="arrow" thrust_speed="0" speed_rating="0" missile_speed="60" weapon_length="97" thrust_damage="110" thrust_damage_type="Pierce" item_usage="arrow_right" physics_material="missile" center_of_mass="0,0,0" stack_amount="45" sticking_position="0,-0.97,0" sticking_rotation="90,0,0" rotation="0, -80, 25" passby_sound_code="event:/mission/combat/missile/passby">
                <WeaponFlags Consumable="true" AmmoSticksWhenShot="true" AmmoBreaksOnBounceBack="true"/>
            </Weapon>
        </ItemComponent>
        <Flags Civilian="true"/>
    </Item>

Just change the "stack_amount" parameter to your desired stack amount. Changing other parameters may affect the lethality and flying of the arrows, depending on what you change. I simply copied items of RBM and changed the stack amount without touching the physical aspects of the arrows.