In version 14.10.r12 you could only exclude folders in custom and scheduled scan but not in Real time scanning (files only). Now in higher versions real time scanning only excludes files individually you cannot exclude a folder ever. Mcafee now scans files only when actioned/run and scan does not scan all the files it used to. Scheduled scan does not now have exclusions.
If you have files that you feel are falsely quarantined you can submit them for review as per