I've read that some people have over 100 hrs of volunteer work; does this just include volunteering at the hospital or does it also include ECs (eg. helping out at a retirement home or tutoring elementary kids)?
A few hundred hours total is fairly common. A common number of hrs someone might volunteer would be about 4 hrs/wk for each position for 1-3 yrs of college. This would result in about 150-450 hrs total per activity by the time one applies (assuming volunteering is only done during the school year and not summers). As long as you start early, accumulating a few hundred hours is quite easy with consistency.
I've read that some people have over 100 hrs of volunteer work; does this just include volunteering at the hospital or does it also include ECs (eg. helping out at a retirement home or tutoring elementary kids)?
Working longitudinally over 3 years its pretty easy to accumulate a lot of hours. Back when I applied I worked 5 hrs/week in a free clinic year round - about 1100 hrs by the time I applied (took a gap year), I also did a couple of smaller short term things probably about 400 hrs. That doesn't include my part time job. But I can't sit still to study for any length of time so I stay pretty busy.
However, don't start comparing yourself to others. Pick out some things that you enjoy/care about, do them as often as you can, and get out of it what you can.
At the end your goals are to understand what its like to be a physician enough to coherently explain why you want to be one, and to have passions that make you interesting and the activities to support those passions.