Some info regarding enable & disable chips:

The setting use binary numbering.
1 represent enable
0 represent disable

Example:

Chips numbering   ==> 7654 3210       Decimal
all chips enable    ==> 0000 1111         15   or
                               1111 1111        255

all chips disable   ==> 0000 0000          0     

chip 3 disable      ==> 0000 0111         7    

chip 2 disable      ==> 0000 1011         11  

chip 1 disable      ==> 0000 1101         13  

chip 0 disable      ==> 0000 1110         14  

chip 0 & 1 disable ==> 0000 1100         12


Since there is only 4 chips available so 15 also work