To reproduce:
1. Open attached Unity project "NoiseGen_2.zip"
2. Tools --> Noise Generator
3. Click Regen
4. Observe Console

Expected result: There should not be any logs in the console, because, according to the documentation, Mathf.PerlinNoise can only be in range of 0.0f to 1.0f (in some cases can slightly exceed 1.0f) and the script "NoiseGenerator.cs" script only prompts a message to the console if Mathf.PerlinNoise's value is less than 0
Actual result: Mathf.PerlinNoise sometimes gets a value of less than a zero which contradicts with the documentation

Reproduced on: 5.5.3p4, 5.6.1p1, 2017.1.0b7, 2017.2.0a1