yAs the slide says, “It is same with [0-9]: the set contains already 5 and 9” (I would write “it is the same as”, and think “with” is incorrect English, but maybe that’s some dialect, archaic, or shows my knowledge of English isn’t perfect)

Taken apart

  [       any of
  5       the digit ‘5’,
  0-9     any character in the range ‘0’ through ‘9’ (inclusive),
  9       the digit ‘9’
  ]       end marker for ‘any of’.