Forgive me, this is me being lazy in this post.
I've just changed my chars name, since someone had stolen my original name on my realm from a really old transfer and it became available again. ButtonTimers unfortunately doesn't have profiles, so I can't save it. I can't currently for the life of me remember how the f*ck I configured it to show ISF.
I thought it was Player - Aura - Full Timer (Even tried Fixed) - Warn < Cast Time. But I just cannot get it to work.