I see that Brown became an alternate at some point. An alternate qua alternate would not be paid a supplement when they go on. As an understudy, there is an additional amount. An alternate who also understudies like Brown gets the supplement. One who does not, like Donna Murphy for example, does not.The understudy amounts and structure, andrew, are not what you list. There are 2 separate things: base pay supplements (the calculation of which depends on whether one is a performing understudy or not), and performance supplements, which apply 1/8 of the actor's pay for each performance. A general understudy assigned 3 roles gets no extra on the base. The stuff related to swings gets even more complicated.