Good one!!
Obviously little Mary Potts isnt living with Chris Potts as man ans wife, as she is only 1! I think the enumerator has banded the wrong lines together and he meant to link Chris Potts with Sarah alias Maddox
I would guess that he also means Sarah Maddox alias Potts, in other words she is actually Sarah maddox, because she is married to Alfred Maddox, but sh eis calling herself Sarah Potts, cos she is living with Chrsi Potts as his wife.
Alfred must have been either ignorant or very forgiving, as it appears she has gone back to him by 1891.
That is my guess as to what is going on - but it is only a guess. We will probably never know!