Always needed a second injection after 24 hours as far as I know? Looked on the internet and says the same. The actual substance is really thick and it is not advised to inject more than 5 ml in the same spot due to it creating very sore spots, maybe this is the reason they do it over 24 hours?
Yep think this particular vets is expensive thats for sure, what I do know is they must have charged for a consultation fee as well!!