The UCAT is scored out of 2700 - this is composed of your scores from Verbal Reasoning, Decision Making, and Quantitative Reasoning. For Situational Judgement, you are put in a band from 1 (best) - 4 (worst). Some universities have a cut off for SJ Bands and will not consider applicants below Band 2. 

The UCAT is a multiple choice test that you sit online at one of the approved test centres. You will need to prepare for this assessment as it is sat under tight time constraits. 

Each year, the deciles for the UCAT are shared - some universities will use these deciles to inform who to invite to interview. These deciles change each year depending on the overall performance of people sitting the UCAT each year. 

See here for more info on deciles https://www.medistudents.com/ucat/ucat-decile-ranking