Well, I think the time has value as you are teaching. I'm assuming you are a CFII. If you went to look for another instructing job someday it would be good to be able to document the "sim" instruction time. I agree you don't want to convolute your logbook by in any way showing it under the "total time" column, as that's assumed to be actual flight time of some sort. Personally, I'd have no problem seeing it as "dual given" in a logbook if I was an interviewer, in fact, I'd highly respect the time as I've done some of that and value the experience. But if it makes you nervous putting it in your logbook as dual given, assuming that column should be "flight time dual given", then that's fine. You could easily keep a separate record of it outside your logbook in case you ever interview for another CFII job.