The maximum was likely 568 seats.
It is hard to find a definitive source for this, but it is likely that the 747-400D (Domestic) version had the largest number of seats since it was specifically built for this purpose. This type was used by Japan Airlines (JAL) and All Nippon Airways (ANA). JAL published the number of seats they used in a press release:
The launch customers for the 747-8 were Cargolux and Nippon Cargo Airlines, both air freight operators who wanted the 747-8F. The first orders for the 747-8I didn't materialize until several months later.