What's the difference between a swell and a swell of 2?

What's the difference between a swell and a swell of 2?

Does anyone help describe the parameters and return values of this interface (https://www.windy.com/forecast/v2.2/ecmwfWaves)?
such as :
https://www.windy.com/forecast/v2.2/ecmwfWaves/26.590833/120.149722?source=detail
What's the difference between a swell and a swell of 2?
