You will never get a higher UAI from misadventure or EAS. EAS is completely separate from the Board of Studies and while misadventure forms can be used as evidence for the EAS application it otherwise has little to do with EAS.
If you have an issue that has affected you during years 11 and/or 12 (examples include having disease, financial difficulty, death of a family member, being a carer for someone with an illness or being schooled in a rural area), then you may be eligible to apply for the EAS(Educational Access Scheme) with UAC. Once UAC approves your scheme it is sent off to the unis(all the unis that work through UAC support it excepting Aust. Maritime College) who deal with it in their own individual way. Some unis will work under the allocation method, whereby they set aside so many places for EAS people who must then compete with each other for placement, this allows the UAI to be lowered a certain amount - never more than a preset level by the uni. The other method is 'bonus points', where at this given uni they will deduct a certain amount of points off of *any* course regardless of competition. Unis will also vary widely in how much they offer you and whether they offer you EAS at all - USYD could very well accept your EAS application while UWS may not and vice versa.