statements are key ingredients for making what's known as "Spaghetti code".
Such code is hard to read, refactor and therefore maintain.
Noncompliant Code Example
With the default threshold of 3:
If condition1 ' Compliant - depth = 1
If condition2 ' Compliant - depth = 2
For i = 0 to 10 ' Compliant - depth = 3, not exceeding the limit
If condition4 ' Noncompliant - depth = 4
If condition5 ' Depth = 5, exceeding the limit, but issues are only reported on depth = 4