In VII.97 Herodotus explicitly uses 'kerkouroi' (corn-ships) as part of the 3,000. Translating this as 'light galleys' looks like extraordinary carelessness, but there may be a reason, if an incorrect one.
When he gets to VII.184 Herodotus designates these vessels as 'pentekonters', an evident mistake, but perhaps the source of the 'light galleys' translation if the translator was backtracking to apply consistency at the expense of accuracy. We do get the incidental information that a pentekonter of the period had an 80-strong crew, presumably 50 rowers and 30 fighting men (or less than 30 plus some sailors), so the mistake is not entirely wasteful. It does however mean that Herodotus has overestimated the total of naval personnel by 240,000 and hence total personnel by 480,000, bringing his estimated overall total down to 5,043,220.
In VII.186 the ships from VII.97 are added back in as 'sitagōgoisi akatoisi' (light corn-ships) and 'ploiosi' (vessels), but not numbered. They are part of Herodotus' conjectural addition of one non-combatant per combatant.
As to make up and operation of the "sealift command" of the Persian forces, a quick visit to the other thread will show that Patrick and I have totally different views of the practicalities of operating supply ships over beaches
We haven't really looked at fleet operations in the campaign, though - we've concentrated on the army.
Whatever the real or apparent difficulties, the triakonters and pentekonters would seem ideal for ferrying loads to the beach, unloading quickly (their large crews being a distinct asset for this) and going back for another round, while the horse-transports, with their loading ramps, have interesting possibilities for unloading cargoes directly onto beaches swiftly and with style. So we can at least say that the accompanying fleet is very well configured for naval supply of a large army. Whether we can put any figures to this is another question.