You have to edit the file jetpack-carousel.js line 103 change the text in placeholder=”Your translated text goes here”. There you can put your text. If you update the plugin its most likely that this file will be overwritten and you’ll have to do this process again. The developer of the plugin should have provided some extra javascript with the translatable strings, so we could set them as we wish. As we say in Portuguese “that’s what we have for today” (I hope that mean something in english)!
If you speak Portuguese you can check this issue in my blog.