This site states this directly on its own quality badge: GMP Certified — brand-stated Good Manufacturing Practice compliance for the production facility.
GMP, or Good Manufacturing Practice, refers to standard quality and consistency procedures at the production facility — worth reading as a separate claim from FDA facility registration, even though this site lists both together among its four badges.
Like the other quality badges on this site, this is described as a brand-stated claim rather than something this site independently audited — worth reading it alongside the FDA-registered-facility distinction for a fuller picture.