Re-torquing/re-lashing

No, it's not a Roxy Music song. Anyway, new head gasket, been duly retorquing the head nuts and relashing the valves. Had thought the retorquing would cause the lash to increase, be looser when checked, but just the opposite. I guess I don't understand the geometry of this stuff but if anyone could explain I'd be interested. Thanks - Brian

In tightening the head down to the cases, the space between the top and bottom is compressed. Any gaps that existed are taken up, including potential head gasket leaks and valve / rocker lash (as well as cam/follower, follower/pushrod, and pushrod/rocker).

Thanks GrandPaul.