What is the right size for graphic banners?

[blueglass22]

I'm adding new banners to the main slider in the page. But I realize that the images attach themselves to the top leaving a very big space
at the bottom.
What is the right image size to fit the banner space? Width x Height

[Basara]

The demo slider have the 600x300 px images
https://demo.abantecart.com/

[blueglass22]

Thanks for the reply, but I think you talked about the text banner. I meant the graphic banner. The Images attach themselves to the top leaving a large chunk of space at the bottom.