Why Nuzzel Raised A Second Seed Round

What is the difference significant between Second Seed and Series A?

In my experience (two startups ago we had many of the same seed investors as Nuzzel), the difference between seed and a proper Series A comes down to data. Our seed investors invested primarily on the "story". The Series A conversations focused on the metrics. I forget who said it first, but "nothing screws up a good story like data".