ETC Cobalt Family v7.0.0 - Manual (Page 493)

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You can use the numbering functions that allow you to select every 2nd, 3rd or Nth together with the
random function.
Function Soft Key Feedback
Random 2nd [RANDOM] & [SELECT_2nd] Every random 2nd
is selected.
Random 3rd [RANDOM] & [SELECT_3rd] Every random 3rd
is selected.
Random Nth [RANDOM] & [SELECT_Nth] Every random Nth
is selected.