The node provide two outputs. The first output emits a msg.payload of 1 or 0 every minute depending if day-time (1) or night-time (0).
The second output emits only on the transition between night to day (-> 1) or day to night (-> 0).
As you are using the top output, one payload every minute. Normal.
If you want to have only when it is a transition, down output.