That "dimple" is a tapered center hole, used to steady the piston in a cam grinding machine while it was being manufactured. It serves no purpose once the engine is assembled. Those open holes in the gasket don't correspond to cooling passages in all blocks, so that gasket id made to fit more than one application. As long as the other head/block passages aren't blocked, just ignore the big holes. The gasket will seal properly without them.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!