Advice RE: volunteer assignment

I’ve been volunteering at a rehab hospital for about 6 months now. They have a spinal cord unit and a traumatic brain injury unit, and because I am interested in TBIs, I thought this would be a great place to volunteer. I told the coordinator my career goals and interests, and she placed me in the physical therapy unit that handles mainly joint replacement pts. Although I’ve worked in healthcare for over 15 years, this is my first hands-on experience with patient contact. I’ve learned many things about rehab and wheelchairs, etc, and I’ve seen some interesting cases. The pts cycle through every hour, so my basic function is to wipe down the mats before the next wave of pts. I’m furiously busy for about 10 minutes and then stand around for the next 50! I’m bored to tears! I ask for additional things to do, but there really isn’t much. And some of the therapists have a bit of an attitude with me since they found out I’m pre-med and not pre-PT. Is this typical? How long do I need to stay in one assignment? Is it ok to ask for experience in another department? Should I look for another facility? I had the first meeting of my school’s pre-health committee and the advisor stated that letters from volunteer coordinators are not advantageous, so I assume that my hours will be self-reported on AMCAS. That being the case, it seems that I will just be including the total lump of my hours (?), so do I need to show longevity in one department? Any advice?

I meant to put this in “pre-med” general discussion - will re-post there.