Why does the 30A GE Wattstation require a 40A breaker?

[Publius]

I'm not an electrician, so maybe I'm just showing my ignorance, but why does the 30A GE Wattstation suggest that we used a 40A breaker? :?:

 

[Weatherman]

The GE Wattstation is considered to be a "continuous load". Therefore, the breaker must be 125% the rating of the device. 30x1.25 = 37.5, so 40A is the next appropriate breaker size.

 

[Publius]

The GE Wattstation is considered to be a "continuous load". Therefore, the breaker must be 125% the rating of the device. 30x1.25 = 37.5, so 40A is the next appropriate breaker size.

Thanks!