This file defines which spells are given to priest-types on level-up. Priests gain spells SPPR[1-9][**] where ** is the column from this file.
This file seems to have no effect on mages.
In IWDII we have:

2DA V1.0
0
           1          2          3          4          5          6          7          8          9          
WIZARD     22         28         23         28         26         30         19         10         11         
CLERIC     17         22         26         28         24         16         29         0          0