Litipk\BigNumbers\Decimal::sub PHP Method

    public function sub(Decimal $b, $scale = null)
    {
        self::paramsValidation($b, $scale);
        if ($b->isInfinite()) {
            return $b->additiveInverse();
        }
        return self::fromString(bcsub($this->value, $b->value, max($this->scale, $b->scale)), $scale);
    }

 private function floorModulo(Decimal $x, Decimal $y) : Decimal
 {
     return $x->sub($y->mul($x->div($y)->floor()));
 }