Receive "value must be numeric" when trying to create SQL backup job
Most likely, you have selected the Instance as part of the backup, and not just the database. Recreate the job and expand the computer name, then expand the instance, then only select the database names that you want to backup.
In some cases, it is either the browser or browser cache. You can clear the browser cache or try a different browser. Finally, be sure you are following Microsoft best practices for creating the SQL instances, table names, and and columns.
Information selected or passed contained characters that are not valid.