Just ran t5 trigon alert with 4 toons 103+ and got 51p , so at 25% from the 206 alert total then we ran inner t4 alert, same group, and got 76p... obviously more than the 51p from higher content. SethZoulMonEl rightly pointed out that this is indeed 25% of the raid total of 305p, so in a nutshell the inner alert is pulling the inner raid prestige value.
