This file defines minimum stat required to be able to dual-class.
The first row (titles of columns ) is filled by the names of defined characteristics of PC (like MIN_STR = minimal strength ).
The first column is filled by class/kits names.
The crossings of the certain identifiers indicate if class/kit could be used with the characteristic of PC - used for character creation.
In BG1 TotS we have:

2DA V1.0
0
           MIN_STR    MIN_DEX    MIN_CON    MIN_INT    MIN_WIS    MIN_CHR    
FIGHTER    15         0          0          0          0          0          
PALADIN    15         0          0          0          0          15         
RANGER     15         15         0          0          15         0          
MAGE       0          0          0          15         0          0          
CLERIC     0          0          0          0          15         0          
DRUID      0          0          0          0          15         15         
THIEF      0          15         0          0          0          0          
BARD       0          15         0          0          0          15         
ABJURER    0          0          0          15         0          0          
CONJURER   0          0          0          15         0          0          
DIVINER    0          0          0          15         0          0          
ENCHANTER  0          0          0          15         0          0          
ILLUSIONIST 0          0          0          15         0          0          
INVOKER    0          0          0          15         0          0          
NECROMANCER 0          0          0          15         0          0          
TRANSMUTER 0          0          0          15         0          0