awk -v"MAX=20" '
BEGIN   {delta = (delta=="")?2:delta
         MXBCK = (MAX / delta) + 1
        }

        {bucketNr = int(($1+delta) / delta)
         if (bucketNr > MXBCK) bucketNr = MXBCK
         cnt[bucketNr] += $2
         TOT           += $2
         numBuckets = (numBuckets > bucketNr ? numBuckets : bucketNr)
        }

END     {for (bucketNr=1; bucketNr<numBuckets; bucketNr++)      {end = beg + delta
                                                                 printf "%2.0f - %2.0f\t%d\t%4.1f%%\n", beg, end, cnt[bucketNr], cnt[bucketNr] / TOT *100
                                                                 beg = end
                                                                }
         printf "   > %2.0f\t%d\t%4.1f%%\n", MAX, cnt[MXBCK], cnt[MXBCK] / TOT *100
         print "---------------------"
         print "Total:", TOT
        }
' file
 0 -  2    0     0.0%
 2 -  4    0     0.0%
 4 -  6    0     0.0%
 6 -  8    0     0.0%
 8 - 10    5     6.8%
10 - 12    5     6.8%
12 - 14    13    17.8%
14 - 16    0     0.0%
16 - 18    23    31.5%
18 - 20    19    26.0%
   > 20    8     11.0%
---------------------
Total: 73