One can't simply add up that short data
The daily shorting data reported by FINRA is an aggregate of all the shorting up to the end of that day, and isn't meant to be added together over a series of days.
It's similar to the daily Reg SHO reports, in that today's report takes the number from yesterday, then subtracts covers and adds new shorts.
Here's your example, and I've added a column
Date..................Short Vol...Total Vol..................Short %.........Change Vol
20151008|BIEL|33809366|..|58774636.....Thursday...57%
20151009|BIEL|255619129|..|423147135....Friday...60%.......rose 364.4M
20151012|BIEL|230115065|..|718324699....Monday...32%.......rose 295.2M
20151013|BIEL|173569732|..|545892916...Tuesday...31%.......fell 172.4M
20151014|BIEL|156547732|..|454205433...Wednesday...34%.......fell 91.7M
So by Wednesday, Oct 14, the aggregated number of daily shorts was 91.7M lower than the day before, but still approximately 400M higher than it was on Thursday, Oct 8.