But you do have two surfaces: inside and outside. The Klein bottle only has one.

the object that have only one surface, but no edge, is a klein bottle. A sphere (or if you will, a ball pressed into a bowl shape) has two surfaces - the outer one, and the "inner" one (where the "inner one" is the one you cannot reach from the outer one, as tho the surface is infinitely thin, and the bowl/sphere is made of hollowness.

It has an inner surface and an outer surface, the same as a sphere. They didn't say it had an edge.

Yes, in the video I'm talking about https://www.youtube.com/watch?v=AAsICMPwGPY

he says that a bootle has an edge (~3'40).

A sphere does not have an "inner surface", it has just one surface. So does a potato. If you go from sphere to potato to bowl, when does an edge appear and does it have to appear, is my question.

Well. A bottle is topologically equivalent to a solid sphere. It only has one surface.

The inside and outside of a bottle is just by convention. Usually you would say something is inside the bottle if it is past the opening. (As he says in the video.)

So your example with the bowl-shaped "sphere" is correct. There's no clear limit when a bottle has an inside and an outside.