Ann: Company Presentation - December 2021, page-47

The information from release announcement was no clear enough. Basically, profit = price - cost (production, shipping, tax etc). Since the cost other than shipping are relatively similar throughout the year, the time to company to sell IO is when the IO price increase or shipping cost decrease. That is to make a substantial profit for company (and SH). Event hough freight cost had decrease from its peak on Sep-Oct periods, current freight cost still double from previous year.
IMO, the key here is a "substantial profit". That's make me happy to hold longer and accumulate more whenever possible.