Michael has given you a good summary, oldmatty. In the end, if it cuts each leaf of grass at least as cleanly as a pair of scissors would, it is correctly adjusted. Obviously it will remain sharp and adjusted longer if there is no contact - but the acid test is what a blade of cut grass looks like through a magnifying glass.
I suggest that you should not run your freshly sharpened reel at all, with contact, or you'll have damaged its new edge before you even begin. Deejay is sure to log on at some point in the day and will be able to make specific recommendations, but meanwhile please don't blunt the blades before he gets the chance.
