Your WordPress core files are clean and were not modified.
Changes in the integrity of your core files were detected. There are files that were added, modified, and/or removed in the core directories /<root>, /wp-admin and/or /wp-includes. You may want to check each file to determine if they were infected with malicious code.
/<root>
/wp-admin
/wp-includes
The action to restore the content of a file will only work with files that were modified or removed, for files that were added you must either remove or mark as fixed. Files marked as fixed will always be ignored from the integrity checks, an attacker can use this option to hide a malicious file, so always check what files are being ignored.