The - so called "NAK"

Gee.. I really don't understand Malaysians lah especially the "Malays". They intend to have this habit of using "NAK" but ectually they DON'T or they HAVE done it. Well, I am so sure that all of us [or maybe majority of us] will say this;

"Nak sampai dah"

Or maybe;

"Nak pergi dah"

BUT, what they ectually mean is...

"Jauh lagi ni.. Tak keluar lagi pun. Sabar lah.."

AND;

"Dah sampai dah pun.."

I mean, don't they know what "NAK" means??? Haih, sometimes I really don't understand do they really mean what they say or THEY MEAN IT???