In step 1
You have 4 dots per vertical column and 4 columns
4+4+4+4=16
If you sum the dots you find 16 dots.
In step 2
You have 5 dots per vertical column and 5 columns
5+5+5+5+5=25 or 5 x 5=25 or 5^2=25
If you sum the dots you find 25 dots.
In step 3
You have 6 dots per vertical column and 6 columns
6+6+6+6+6+6=36 or 6 x 6=36 or 6^2=36
If you sum the dots you find 36 dots.
In step 4
You have 7 dots per vertical column and 7 columns
7+7+7+7+7+7+7=49 or 7 x 7=49 or 7^2=49
If you sum the dots you find 49 dots.
In step 5
You have 8 dots per vertical column and 8 columns
8+8+8+8+8+8+8+8=64 or 8 x 8=64 or 8^2=64
If you sum the dots you find 64 dots.
Answer 64 dots