What is a “different file”?

What does the sentence “If you’d like to import a smaller list now, you can upload a different file” mean? What is the definition of a different file?

It’s part of the message “We couldn’t import your subscriber list as you’ve hit the 100 email limit for our free plan. The good news? You can upload a list of any size after upgrading to any paid plan. If you’d like to import a smaller list now, you can upload a different file.”

Thank you,

Laurie

The page I need help with: [log in to see the link]