The Fredkin style rules contained in the menu require the Wolfram
number of a 
rule, a single number in the range 0, 65,535.
It is received, without echo and without corrections, by the option
w, to be displayed in the upper right hand corner of the screen.
If it was entered incorrectly, it is easy enough to try again.
The options u and v generate one or the other of a pair of mutually reversible rules, but they only create a rule table in the computer's memory; INSERT is needed to transfer the rule to the CAM .
The option R should be used instead of s or S to run the evolution; it guarantees the even number of generations which must be respected on account of the parity of the Margolus neighborhood. Such being the case, the undoing of an evolution can be observed easily.