I hold two basic opinion that
(1) Every line segment has two endpoints.
(2) The endpoint of a line segment is part of it.
So as for the line segment corresponding to [0,1], if we remove its right endpoint, which number corresponds to the right endpoint of the new line segment? I don't think the number is still 1, because we have already removed the point corresponding to 1, thus created this new line segment, the point 1 is not part of the new line segment, so according to my opinion (2), I don't think the number is 1.
Update: A bounded continuous segment in a line is my definition of "line segment"
Update: I think I solved my question , see answer below
Your second "basic opinion" is simply untrue. The number is $1$.