This file defines minimum stat required to dual-class with this 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 IWD: TotL we have:

2DA V1.0
0
           MIN_STR    MIN_DEX    MIN_CON    MIN_INT    MIN_WIS    MIN_CHR    
FIGHTER    17         0          0          0          0          0          
PALADIN    17         0          0          0          0          17         
RANGER     17         17         0          0          17         0          
MAGE       0          0          0          17         0          0          
CLERIC     0          0          0          0          17         0          
DRUID      0          0          0          0          17         17         
THIEF      0          17         0          0          0          0          
BARD       0          17         0          0          0          17         
ABJURER    0          0          0          17         15         0          
CONJURER   0          0          15         17         0          0          
DIVINER    0          0          0          17         16         0          
ENCHANTER  0          0          0          17         0          16         
ILLUSIONIST 0          16         0          17         0          0          
INVOKER    0          0          16         17         0          0          
NECROMANCER 0          0          0          17         16         0          
TRANSMUTER 0          15         0          17         0          0