A problem with quantization of HSI space

here H(0-360), S(0-1),I(0-1) . i want to divide in this way 12*3*3 .12-h,3-s,3-i

if I want to convert RGB in 4*4*4 , i am working like this

lbin=4;

 abin=4;
 bbin=4;
l=256/lbin; 
   a=256/abin; 
   b=256/bbin;
  for(x=0;x<M;x++)
  {
       for(y=0;y<N;y++)
      {
        

                              l1=LstarM1[x][y]/l; 
    
         a1=aM1[x][y]/a; 
        
          b1=bM1[x][y]/b;
        
           
          bin=(l1*pow(lbin,2))+a1*pow(abin,1)+b1*pow(bbin,0);
        
          count[bin]=count[bin]+1;
          colorBin[x][y]=bin;
          
         
         
          
            }//y
        }//x

but i am trying to do this way in HSI , i am not getting the exact bins means 108 . when i am divide into 8*4*4 . use abin instead of lbin in following then i get the exact bins according to values and l=360/8

 bin=(l1*pow(abin,2))+a1*pow(abin,1)+b1*pow(bbin,0);