Professor David Crystal

Hi,,, today I was listening to Professor David Crystal. I choose “thirty-something” …
Firstly I listen, it’s so difficult to understand what David Crystal tell about. But, when i listen again and again,, I can understand. “thirty-something” is referring to people an unspecified age between 30 and 40, for example when u ask someone about their age and he/she say thirty-something. It’s mean her/his age between 30-40.ermm..may be 35.. now, we can see not just thirty-something we use, but also twenty-something, sixty-something and so on… ok, that’s all what i’m understand about this topic..
Thank you…