Sometimes I see recipes that call for both LME and DME to be used. Usually, it's LME for the bulk of the extract, and then a smaller amount of DME. Why would you do this? The only thing that I can think of is maybe it has to do with the size of the containers that you commonly find the extracts in - for example, if you needed 7 lbs LME, it would be a shame to have to by a 6 lb container and a 3 lb container and toss the other two pounds. So maybe you would want to use a 6lb container of LME and then (part of) a 1lb bag of DME to finish it off. It wouldn't really make a difference if you used all LME or all DME, would it? I can pour LME into my own containers at my local HBS and pay by the pound, so it would be no problem for me to get the 7lbs of LME.
It's not a big deal, I'm just curious why a recipe would call for both.