This file defines strength influence on characters abilities like allowable weight that could be taken by character or to hit bonus.
The first row (titles of columns ) is filled by the names of features affecting of PC (like TO_HIT = to hit bonus ).
The first column is filled by value of strength of character.
The rest columns are filled by values for given strength - pretty obvious from names I suppose.
In BG1 TotS we have:

 2DA V1.0
 0
           TO_HIT     DAMAGE     BEND_BARS_LIFT_GATES WEIGHT_ALLOWANCE
0          -20        -20        0                    0
1          -5         -4         1                    1
2          -3         -2         2                    3
3          -3         -1         3                    5
4          -2         -1         4                    15
5          -2         -1         5                    15
6          -1         0          6                    30
7          -1         0          7                    30
8          0          0          8                    50
9          0          0          9                    50
10         0          0          10                   70
11         0          0          11                   70
12         0          0          12                   90
13         0          0          13                   90
14         0          0          14                   120
15         0          0          15                   120
16         0          1          16                   150
17         1          1          18                   170
18         1          2          20                   200
19         3          7          50                   500
20         3          8          55                   600
21         4          9          60                   700
22         4          10         65                   800
23         5          11         70                   1000
24         6          12         75                   1200
25         7          14         80                   1600