Take a look at bgs advice on which wormers as they often are more clued up than the vet, unless you have a goaty vet!
Statutory milk withdrawal when there isn't one on the bottle for that species is set at 7 days, meat withdrawal usually 28 days. However, when you look at some drugs, they have a longer meat withdrawal than 28 days for a different species, or the 7 days for milk, so you have to be sensible.
Triclabendazole is an example where it's 60 days milk withdrawal and 2 days after calving for cattle, so that's what I use for goat withdrawal.
Clear as mud, sorry, but that's legislation for you!