How to change dummy text in post title box

Hi,
How could I edit the dummy question in the title box field of a post?
I mean the text you have configured as "Keep your title simple and short..." in this forum

In a Spanish I get the text "What is in your mind?" (but in Spanish) which it is not the text I would like to see in my web, which is for a Q&A medical service.

Thanks in advance for your help.

Regards,
Juan