Continuing their decline since mid-July, the number of BlackBerry Ltd. (NASDAQ: BBRY) shares short fell more than 10% in the most recent period to almost 87.75 million shares. That was still 16.8% of the total float, and it would take a little more than 10 days to cover all short positions. The days to cover was 21 in mid-August, on a year-to-date low average daily volume. BlackBerry recently posted a bigger than expected net loss, and short sellers watched the stock tumble more than 18% during the two weeks.