You can get the historical numbers from the NASDAQ site:
Settlement Date / Short Interest / Avg Daily Share Volume /Days To Cover
9/15/2015 126,661,452 3,733,101 33.929286
8/31/2015 126,699,272 5,271,518 24.034685
8/14/2015 121,777,505 5,626,630 21.643063
7/31/2015 116,059,587 6,123,132 18.954285
7/15/2015 112,846,501 4,415,939 25.554361
6/30/2015 115,084,784 5,340,302 21.550239
6/15/2015 120,425,827 14,899,766 8.082397
5/29/2015 131,158,892 10,605,477 12.367090
5/15/2015 112,949,758 7,816,490 14.450189
4/30/2015 100,934,186 4,967,815 20.317622
4/15/2015 96,880,182 3,267,203 29.652330
3/31/2015 95,717,587 3,373,112 28.376641
3/13/2015 90,882,779 6,976,436 13.027107
2/27/2015 90,734,471 5,326,385 17.034907
2/13/2015 86,114,829 9,260,731 9.298923
1/30/2015 80,678,801 4,863,394 16.588991
1/15/2015 76,855,662 4,475,961 17.170762
12/31/2014 75,654,134 4,169,132 18.146255
12/15/2014 78,755,843 3,923,230 20.074236
11/28/2014 79,738,493 3,623,731 22.004529
11/14/2014 82,431,190 4,782,518 17.235939
10/31/2014 82,027,036 5,101,317 16.079580
10/15/2014 78,219,262 7,599,961 10.292061
9/30/2014 78,579,323 5,418,887 14.501008
9/15/2014 74,292,867 5,182,576 14.335123
Link:
www.nasdaq.com/symbol/mnkd/short-interest