subscriber issues

Hi, I have set up a Ecommerce site with a blog section three days ago. Right after I set up the blog, there are many subscribers with only email addresses without any other information input to my site and they did not buy or do anything.

Can anyone tell me what is going on there? Should I be worried about anything or I should adjust the settings to block them? This is my first time publish a word press site. Thank you in advance for you help.