any time you get a space between two numbers. 12-3.you back the number that has not hit. 35. that would be your first number. when you get another space. 11-13. you add the number 36. a limit of five numbers. stop at a winner and start again. any body test this . good luck.
I sometimes bet the gaps (while waiting for other events). I think Winkel offered a similar method not too long ago. Sometimes it can work like an absolute treat, other times are not so good.
Sounds like the zone of 3.
I believe quite a bit of research went into developing a system but nothing out of the usual came out of it.