I just have a UK share account; I asked my broker what would happen. Answer: from 31st August the new (presumably about 20% of current) share price would be in effect. The new shares to be added to the portfolio are expected on or around 3rd September. Between 31st August and when the new shares are added the portfolio would look like it had declined by 80% in value, and if I wanted to sell shares I could only sell those existing 20% of the total that I had at that point until the other 80% new ones were added. Seemed clear.