They are asking for the maximum depth, at which integer 9 can be present, [1 to 1023] is not like 1,2,3,4,5,6,7.......1023 it can be random but in the range to 1 to 1023 now if we put 1,2,3,4,5,6,7,8,9 in the left subtree and then for satisfying min heap properties, we will start adding 10,11,12,13... like that in right subtree of 1,2,3,4,5.....9 . now we can count the depth which is 8 for the node nine.