Absence Shared Limits

I am trying to create and absence that shares a limit with a previously created absence. Basically, I have an absence created called Family Sick that has a yearly limit of 40 hours. I am creating another absence and when that absence is chosen I want it to reduce the family sick leave limit of 40 hours. I am assuming that’s what the Shared Limit feature does that I came across in Aurena but was struggling to get it connected.