I sent a ticket to uxsoftware to answer this.
While I wait for a response, has anyone else ran into this problem (and possibly found a solution).
With the following RX code
Track last Horizontal Split for 12 spins to Record "PrevSpins" layout
I receive these results for the following winning numbers
Number 1 Split(1-2)
Number 3 Split(2-3)
Number 8 Split(7-8)
Number 10 Split(10-11)
and so on
The results I would like to receive are
Number 1 Split(1-4)
Number 3 Split(3-6)
Number 8 Split(8-11)
Number 10 Split(7-10)
an so on
It seems Vertical Splits are the default, even though I coded for a Horizontal Split.