This is because Micro Python has its own sleep function inside of the micro:bit library that uses milliseconds for duration, with 500 equalling half a second. pin0.write_digital(1) sleep(500) ...

Also, you can tell the micro:bit to pronounce words exactly as you'd like, using 'speech.pronounce' and this pronunciation guide. It's fiddly, but the end result will sound much clearer. Try this out: ...