Ha, ha. I also thought we were talking about Dynamically Loaded Libraries and I couldn't remember a time when Windows would show me how many DLLs I had loaded or stop me with, "Sorry, too many DLLs loaded". :P
What language is that? The only abbreviation I've ever seen is USD (the three non-romance languages I speak a little of use a variation on "dollar" which, by context, is always clearly USD.)
I don't think that's a normal abbreviation. If you Google "DLLS" all the results are about DLLs (and that's obviously not because dollars are an obscure technical term). Maybe you were thinking of USD?