Using a range is practically useless since if, for instance, you use range 10 thru 13. There is an equally probable range on the reverse side that you are eliminating, namely 14 thru 17.
To use a range "smartly" you must start at the center 13/14 pair and fan out on BOTH sides of the range. Smart Ranges are as follows:
13/14
12/13/14/15
11/12/13/14/15/16
10/11/12/13/14/15/16/17
09/10/11/12/13/14/15/16/17/18
08/09/10/11/12/13/14/15/16/17/18/19
07/08/09/10/11/12/13/14/15/16/17/18/19/20
etc......
There are 14 ranges so the optimal range from a statistical aspect would be the 7th set of Sum Total Pairs. The last set above (07 thru 20) IS the optimal range from a statistical aspect. The ST's are color-coded to show the sister sum pairs. The sister sum pairs above the optimal range are also a way to reduce the number of probable numbers to play. Remember they MUST be eliminated or added in pairs.
The optimal range is still a lot of numbers. I will explain now how to reduce these further.
Begin with the last draw for your state and begin eliminating just the optimal sums above. After you eliminate one of the optimal sums, eliminate it's sister sum on the other side. Continue doing this until you have just a few pairs left.
Those left are the sister sum pairs that are both optimal and overdue to hit.