Incorrect Blog ID Error Message

Hi,

Noticed that in the installation instructions' screenshots that the Blog ID section previously showed the URL of the blog to be used as the template so not sure how to fill up the Blog ID field. So I just put my own random code for my reference. However, I've been getting this message:

Whoops! The blog ID you posted is incorrect. Please go back and try again. (Generated by New Blog Templates)

So what's the guideline for that field?

Thanks for the help in advance!