This phone speaks with its built-in text-to-speech engine. Many names in the list are the same engine with different labels, so they can sound identical.
You only get 10 female and 10 male voices if those voices are installed. On Android: Settings → Accessibility → Text-to-speech → Google Text-to-speech → Install voice data. Add English packs (US, UK, India, Australia), then reopen this page.
Tone changes pace and pitch a little. Play uses the exact name and language you picked.
Enter any number for this slot. After every bed on the page has a number, that list repeats forever.
Export on the website, then import in the Android app. Keep your backup private.