I had a similar question regarding some volunteer dentistry work; I have already done 50 hours of shadowing (I know, it's not a lot, but it's something) and am planning on starting to volunteer at a local reduced-fee clinic in my hometown in 2 weeks (I had previously committed to work with a previous employer up to this date, so I couldn't start any earlier). I called UT-the school I REALLY want to go to, since I'm a TN resident-and asked whether I should wait to submit my app until I started and got some dentistry volunteering hours under my belt or if I should go ahead and submit. They said to go ahead and include it on my dentistry/shadowing section, but note in the description that I hadn't actually started the volunteer work yet. In my opinion, as long as you are honest about everything you put on the app and don't try to be dishonest you'll be fine.