Since 1lb equals 454g,500 is a bit over that. 1000g equals 1Kg,or 2.2lbs. I gave that range to give a little choice as to ABV & how much thinning of the hop profile you're willing to put up with. So you could add the 1Kg of DME & the 300g of maltodextrin for more body,flavor,& a bit more ABV.
By the way,the Heritage Lager uses a true lager yeast,so you'll need lower ferment temps.