These numbers are NOT the aggregate short sales.

They are the numbers of shares sold short on that particular day.

Yes, 8.8m is a significant increase in the number sold short on that day (double the previous day) - but until the aggregate data comes out for 2nd September (T+4) - there is no way of knowing how many of these were covered on the day and whether the aggregate jumped up on 2nd September.

Short data is also notorious for being incorrectly reported on a regular basis. So be wary of any "out of the ordinary" changes.

I don't track PLS shorts in detail because at less than 1% of total shares on issue its pretty irrelevant. But if you want to get a full understanding of how they work, there is a very detailed thread on the stock PNV which i Also hold and which is heavily shorted.