How do I change the damage of my mob's ranged attack?

Hello everyone! As the title says, I am creating a mob that uses a ranged attack, the projectile is an arrow but rendered as a Popped chorus fruit.

Well, the problem is that I do not know how to change the damage the "arrow" does to the target.

I am not an expert in Java (I barely understand it) and I tried writing things in the code like: this.setDamage = 20D and somethings like that, but I always get recompilation errors.

These are the projectile's parts of the code:

First one:

public static class EntityArrowCustom extends EntityTippedArrow {
        public EntityArrowCustom(World a) {
            super(a);
        }

        public EntityArrowCustom(World worldIn, double x, double y, double z) {
            super(worldIn, x, y, z);
        }

        public EntityArrowCustom(World worldIn, EntityLivingBase shooter) {
            super(worldIn, shooter);
        }
    }

Second one:

public void attackEntityWithRangedAttack(EntityLivingBase target, float flval) {
            EntityArrowCustom entityarrow = new EntityArrowCustom(this.world, this);
            double d0 = target.posY + (double) target.getEyeHeight() - 1.1;
            double d1 = target.posX - this.posX;
            double d2 = d0 - entityarrow.posY;
            double d3 = target.posZ - this.posZ;
            float f = MathHelper.sqrt(d1 * d1 + d3 * d3) * 0.2F;
            entityarrow.setThrowableHeading(d1, d2 + (double) f, d3, 1.6F, 12.0F);
            this.world.spawnEntity(entityarrow);
        }

In conclussion, what do I have to do in order to, for example, increase the damage dealt by the mob when it shoots?

Thanks for reading!