Welcome to the Forum!
You can learn to recognise individual hogs by their natural markings. It needs a bit of close watching, but not as hard as it sounds. I wrote some tips a while back:
But then you will know how many are visiting. As I understand it, ideally, you would record the total number of individual hogs that visited in either front or back. So not how many visits there are – some hogs will probably visit multiple times.
It’s really better to feed cat/dog/hog food or cat/kitten biscuits and only use calci-worms as a garnish, otherwise it’s encouraging the hogs to eat just them and they miss out on other nutrients. Cat/kitten biscuits are quite a convenient way to feed them and easily available.
Good luck and happy hog watching.