Random Matrix didnt understand a part

#1

in random matrix as we made Matrix=np.random.random((2,3))
a matrix but if we update it why we didnt write
Matrix[2,1:] =1 as sir said it and then he wrote Matrix[1,1:]=1
as row start from 1 not from 0

#2

For rows and columns both , the indexing starts from 0 not 1 , hence the only row indexes which we have are 0,1 and there is no row with index 2 , hence sir wrote 1 in rows parameter and not 2.Below are the indexes of row,column for the martix
[(0,0) (0,1) (0,2)
(1,0) (1,1) (1,2)]