From what I hear, 4U maths are Ruse is very competitive (apparently their cohort average is 90+), so there would undoubtedly be several people on the same whole and maybe decimal mark, so what happens there then. Apparently there is around 100 students in 4u at Ruse, and they are all competitive, so the probability of 2 people being on the same decimal mark is somewhat high.
And from what I hear, there are such things as tie ranks. Say for example, Bob and John were tie first for English. Their marks will be submitted as tie first, and BOSTES will recognise this. After sitting the HSC exam, we know that the internal part of your HSC mark comes from your rank, well for Bob John, if Bob gets 98 and John gets 97 in the HSC, then their internal part of their HSC mark will be an average between Bobs and Johns mark (assuming Bob came first and John came second in the HSC). So if there is a system for tie ranks, then what's the issue with people being tied at a certain rank?