Revisions cover additional changes to an already delivered rig — not bug fixes. If there are skin weight issues, deformation problems, or anything not working correctly as delivered, I will fix it at no revision cost. That's just part of the job.
A revision is used when you request something new or different from the original scope: a different mesh, model changes, new facial expressions, different rigging features, added controls, or anything that wasn't in the original brief.