Subwords means letters must be consecutive as in the word. Since, the given word has 13 letters we can have
13 subwords of 1 letter
12 subwords of 2 letters
11 subwords of 3 letters
....
1 subword of 13 letters
So, total number of subwords = 13 + 12 + ... + 1 = 13 * 7 = 91
No two consecutive letters are repeating in the given word. But there are 3 A's, and 2 I's. So, 3 subwords of length 1 are counted extra. So, total number of distinct subwords = 91 - 3 = 88.