A post from when they were released in the Patreon says 60 are available. In a reply (https://itch.io/post/10866605) the dev mentions they are unlocked from the girls, picking everyone at least once in the beach, and completing the pool. I have done the latter two and have yet to complete the former, but even adding up the missing ones from the currently lewdable girls (blowjobs and have sex) they don't add up to 60. I don't know what else you have to do. That's all I can help you with