Apparently its around 280, one would estimate somewhere over 340 in normal circumstances, however just a hunch but as NI students pay only 1/3 fees i would imagine the number of offers / places would be lower than other universities because of this, might be wrong though.
"The Centre for Medical Education (CME) is responsible for the organisation, management and delivery of the medical course at Queen's. Medicine has been taught in Belfast since 1821 and there has been a Medical School at Queen’s University since 1849. The five year course in Medicine has an intake of approximately 280 students, including school leavers and graduates. Our aim is to educate individuals who at all times put the consideration of patients as their first priority."