Blogposting schema

Hi,

If you have enabled blogposting schema on a certain post and click the Modify Blogposting Schema Output’ button, you get the option to ‘Add Blogposting Items.’ What other items can we add here? Could you please explain it with an example.

Moreover, while modifying the schema, how many keywords you can you add in the keyword field? and if you can add more than one keyword, do you separate the keywords with a comma?

Regards,