I ask more experienced comrades to explain this behavior of the function.
Answer 1, Authority 100%
by default searches for the maximum element index (in the plane), that is, roughly speaking, as if you are just
[10, 11, 12, 13, 14, 15]
np.argmax (a) and displays this index 5.
Axis parameter is specified, it is searched for a
(0-x, 1-y) coordinate axes (0-x, 1-y) .
X you have three meanings, so it has brought the indexes of maximum elements relative to each
X (there are 3). Regarding Y them 2.