nvcc loop unroll pragma and nested loops not unrolled, not an innermost loop

Accelerated Computing CUDA CUDA Programming and Performance
1

Hmm I think I have not got this straight but would still be interested in your comments

I have a pair of nested for loops:

for(int c=0; c<4; c++){
...
  for(int b=0; b<4; b++){
  ...
  }
...
}

I get a warning from nvcc (5.0) saying
Advisory: Loop was not unrolled, not an innermost loop
if the #pragma unroll on the inner loop specifies a value
smaller than 4 and if there is a #pragma unroll before
the outerloop. So the easy solution is to remove
the numeric value after both #pragma unroll

Is my understanding correct?

As always any help or comments would be most welcome
Bill