Best explained if you replace the dots with numbers
123
456
789
1st, go diagonally from top left to bottom right 159
Then, bottom right vertically and past the first line 963, and above that
Diagonally down to left through 24 and past until even with the last line
To the right through 789
For the first one, Bill got a 4 foot box and put the pole in diagonally
For the second, they have to both be true, since you know that one box has $1 million. So, open box B