Being exact, a "standard" bottle encloses a volumne only if you put a cover on it.
The same applies to the Klein bottle. If you cover it at the "green end" (see aboves video) you will be able to distinguish "inside the bottle" and "outside the bottle" and thus the Klein bottle encloses a volumne in the same sense a "standard" bottle encloses a volumne.
Being exact, a "standard" bottle encloses a volumne only if you put a cover on it.
The same applies to the Klein bottle. If you cover it at the "green end" (see aboves video) you will be able to distinguish "inside the bottle" and "outside the bottle" and thus the Klein bottle encloses a volumne in the same sense a "standard" bottle encloses a volumne.