Bristol is in the top 3 universities in the country which helps make it the most oversubscribed university in the country. As said already, there is an average of 10 applicants for every place. For things like vet science you will be looking at even more than that, perhaps even as many as 20 applicants per place, but that is the hardest subject in the country to get in to, so don't let me put you off.
The university does give out more offers than places because invariably some people will reject them to go to oxbridge or somewhere else, but it isn't a huge amount. You could simply be looking at an extra 30% of offers made out of the total number of places. All universities do it, some more than others and it all depends on the course. Something competitive, like vet science, at one of the better unis like Bristol, will have less offers rejected by potential students, so they can make fewer offers. RVC for example used to interview 420 people and make about 390 offers for about 250 places, because some of the vet students rejected them in favour of some of the better vet schools(bit debateable).
It usually says in your subject prospectus how many applicantions they get, how many interviews(if any are made) and how many offers are given out.