I've just bought my first computer, a Cressi Leonardo (I had been hiring computers at the dive centres so far), as I found it new for slighly over 100, which was a good bargain. But there's something about it I don't understand: the PLAN menu. It's supposed to be used to plan my dive, but as I understand it, all I can do with it is telling the computer what the maximum depth will be, and it tells me how long I can spend down there without getting into deco (time which will later on be adjusted by the computer, as I won't spend the whole dive at the maximum depth). Is that so, or is there anything else I should be doing with that menu? It looks a bit simple, as I already know those times according to the dive tables, since my dives have always been more or less the same depth so far and anyway I run out of air before reaching them, but maybe that's all there is to that menu.

Thanks!