Translation:Both girls wear a white outfit.
The audio says "indosSAno". But according to Maiden & Robustell's "A Reference Grammar of Modern Italian": "3rd person plurals of verbs ending in -ano, -ono, -ino, -ero, and first person plural subjunctive forms in -ssimo have prepenultimate stress (’parole sdrucciole’)", i.e. inDOSsano). While there are undoubtedly various irregularities in the various forms of spoken Italian, surely it makes sense to make sure that learners encounter the standard form first.
I was thinking the same thing, and came here expecting a discussion about "both" vs. "each". Though I'm guessing the grammar Italian version of the sentence is correct, the English version (while someone saying it that way would likely be understood) leaves something to be desired.
There was a similar comment in another lesson, something about animals having a soul/souls. According to a native Italian speaker "Entrambe le ragazze indossano costumi bianci" would mean that each girl is wearing more than one white outfit in Italian. Personally, I've come to think that either "both are wearing white outfits" and "both are wearing a white outfit" as natural English and getting the meaning from context without thinking about it much.