Hi,
Using a Wait block immediately after the entry node would be better in this case....it would allow you to specify the exact number of days before the next action in your Series is triggered.

​@Kulpreet Alagh It's an interesting question, I think there's no clear answer here because both will accomplish your goal. 

If you think you may expand the Series later with earlier messages then maybe the option to detect them right away and adding the wait block makes sense so you can add others in the series earlier later. 

But you could always edit the other series later to match what you need either way so I don't see any other reasons why one vs the other is better. 

Hope this helps!