Here's an example where switch B must be on for switch C to activate. If it is, and the time is also between 10pm and 10:30pm EDT in my example, then the rule is true and switch C turns on. If it is not between 10pm and 10:30pm EDT, but switch A was turned on, then the rule would also be true and switch C will turn on.
Since you always want Switch B to be the deciding factor as to whether time of day or switch A will activate switch C (or whatever you want to activate), then it is important to make sure that when you build your rule, switch B must always proceed the AND operator. If it does not, then whatever proceeds AND must always have a TRUE condition, otherwise, the evaluation of the rule will be immediately false, so it won't go on to evaluate any conditions that follow the OR operator.
@bravenel explains it very well in the Rule Machine Introduction.
