The Sutra means “By one more than the previous one”. In simple words, add 1 to the previous number to obtain the next number.
Example
 To get 6, Add 1 to the previous number 5 (5 + 1 = 6)
 To get 26, add 1 to the previous number 25 ( 25 + 1 = 26)
All right, this is straight forward need no brainer. So what’s great about this Sutra? Below are some great usage of this Sutra which makes it amazing.
1) Square of Number ending with 5 such as 15, 25, 35, 45, 95, 105 etc.
Solution is just two simple steps to be done in mind.

Multiple the number except the last digit (5) with the next number.

Write 25 after the result of 1st step.
Example:
 Square of 5 = [0 x (0 + 1)] 25 = [ 0 x 2] 25 = 25
 Square of 15 = [1 x (1 + 1)] 25 = [ 1 x 2] 25 = 225
 Square of 25 = [1 x (2 + 1)] 25 = [ 2 x 3] 25 = 625
 Square of 35 = [3 x (3 + 1)] 25 = [ 3 x 4] 25 = 1225
 Square of 45 = [4 x (4 + 1)] 25 = [ 4 x 5] 25 = 2025
 Square of 55 = [5 x (5 + 1)] 25 = [ 5 x 6] 25 = 3025
 Square of 85 = [8 x (8 + 1)] 25 = [ 8 x 9] 25 = 7225
 Square of 95 = [9 x (9 + 1)] 25 = [ 9 x 10] 25 = 9025
 Square of 125 = [12 x (12 + 1)] 25 = [ 12 x 13] 25 = 15625
 Square of 505 = [50 x (50 + 1)] 25 = [ 50 x 51] 25 = 255025