Create 7 seconds of Black by typing length, not using I & O points

I have made a slug or Black Video and put it in the Source Monitor.

I know I want this to be exactly 7 seconds long. It was brough in at 10 seconds.

Intead of marking in and out points, Is there a way to start 1 second in on the black (for handles), put an In point there and type in 7 seconds and the out point would go to that point making it exactly 7 seconds.

Thanks in advance