"Move forward/ backwards 10 frames" shortcut with numpad not working, please HELP I reli need that!!

I was using AE with my Macbook Air this year, and really need my "page up" & "page down" key back so I can do the "move forward/backward 1 frame" & "move f/b 10 frames" stuffs.

So I got myself this cute lil Belkin numpad (from Apple offical site), and the keys are working well on their own, which means I can move f/b 1 frame with the page up/ down keys.

But I CAN'T do 10 frames while holding "shift+page up", it still moves only 1 frame for some reason. I guess there maybe some extra setting need to be done.

I'll put my shotcut setting captured from AE here as well, it definitly shows the "move forward 10 frames" is enabled when selected "page down".

I hope some of you may know how to deal with it and thanks!!