The 'universes' are loose abstractions, not a defined part of the theory; there's no actual hard distinction between timelines, in much the same way as coastlin

The 'universes' are loose abstractions, not a defined part of the theory; there's no actual hard distinction between timelines, in much the same way as coastlines don't have a defined length. They all blend into each other if you look closely enough. That said, isn't the obvious answer 'all of them'?