From my poor understanding of a Physics degree: the "age" is just counted from when everything existed in the same space, before it's rapid expansion. Although,

From my poor understanding of a Physics degree: the "age" is just counted from when everything existed in the same space, before it's rapid expansion. Although, can you say it expanded? It didn't expand into anything because space does not exist outside of the universe. Or do we say it 'expanded' because the distance between the constituent parts inside of the universe grew? It's not good to think about really.