1st diagram shows 1 square made of matches with 1 extra match stick placed diagonally in the middle.
2nd diagram shows 1 row of 2 squares with 1 extra match placed diagonally in the middle of each square.
3rd diagram shows 1 row of 4 squares with 1 extra match placed diagonally in the middle of each square.
4th diagram shows 1 row of 8 squares with 1 extra match placed diagonally in the middle of each square.