How to transcribe numbers?

Numbers should be transcribed with letters, exactly as they are pronounced by the speaker.

For example: 

"The party starts at six O' clock"

  • [00:00:00] The party starts at six O'clock. ✓
  • [00:00:00] The party starts at 6 O'clock. X

Should I transcribe numbers with or without a hyphen?

Without a hyphen and with a space

  • Twenty one
  • Twenty two
  • Twenty three
  • Twenty four
  • Twenty five
  • Twenty six
  • Twenty seven
  • Twenty eight
  • Twenty nine