Hola Christina

In Spanish there is a recommendation to use numbers with digits instead of in letters in specific contexts and types of texts. It is a preference, so writing them in letters wouldn't be considered incorrect but the preference is digits. In this dictation we went for writing everything in digits as it is stating some facts. Here's what the R.A.E says about this if you'd like to have a look. (I'm afraid there is no transcription in English).

 I hope it clarifies your doubt.

Gracias y saludos

Inma