Contact Form 7 date issue

Hi,
I have just taken over responsibilty for my wife’s business website and noticed that the date required in the output email was listed as “date-10” instead of for example 29-12-2016. I took a look at both the mail tab and the form tab and noticed they were different in that one of them was date-924. More by luck than judgement I made them both the same and everything appears OK now. My question is, what does Date-10 or date-924 mean? I have searched on the internet but can find nothing relevant. Hope this makes sense as I am a newbie when it comes to website management.