How can Aggregate Supply = National Income
Aggregate supply is the total supply of goods and services in an economy given the price level, over a period of time. So, according to this your first statement is correct.

The second statement emphasized on the potential output when all factors of production are fully utilized. It is a long term statement because only in the long run does an economy fully utilizes all the resources.

Here, second is a particular case of the general aggregate supply function definition.