GNU screen: how to check current scrollback value?

Question

In GNU screen, I know that I can change the scrollback (buffer size) using this command:

<Ctrl-a>:scrollback 10000

as well as adding this line in .screenrc:

defscrollback 10000

But How do I check what the current value is? (For clarification, looking at the .screenrc file and locating the line with defscrollback is not the solution I'm looking for.)

Thanks!