The questions on donating to charity only relate to donating money to charity. Some people who have sufficient free time but little disposable income donate time to charities instead. I have seen reports that donating time over money is more common amongst students and people of low income, who seem to be a smaller proportion of the LW diaspora, but it may be interesting to compare donated time vs money on future surveys.

In my experience donating one's time is also seen as being extra keen on that cause, presumably because it requires more effort, and there are certain causes that consider time more valuable than funds (eg local environmental causes, where hiring sufficient people to remove invasive weeds from a local swamp is more expensive than holding a big weeding exercise on a Saturday afternoon).