This filter accepts tickets with selected sum root values. Sum root is a single digit number ranging from 1 to 9. It is calculated from arithmetic sum of ticket's main numbers by repeatedly summing the digits of the sum value until only a single digit number is left.
Ticket sum value for number combination 1-2-3-4-5-6 is 1+2+3+4+5+6=21 so ticket's sum root is 2+1=3.
Ticket sum of ticket 6-20-23-29-38-42 is 158. Its sum root is then 1+5+8=14 -> 1+4=5.
See also Sum Root statistics.