Media Caption

If you want I can help you reduce the size if you would like.

In your Child Theme or CSS Editor Plugin try this code:

.wp-caption-text {
  font-size: 80%;
  font-style: italic;
}

*Note
If your theme has a custom CSS Editor in it, you can also paste the code in there.

Never edit core CSS or PHP files under Appearance > Editor. Your edits will be deleted when the theme is updated.