The correct render sampling amount in the render properties tab. Is there a right or wrong amount? A real Blender newbie here, I'm following a blender tutorial with the final product as an animation. I tried to experiment with the render time during the process by changing the render sampling amount in the render properties tab as shown in the image below (for if I was unclear).



I have done tests with 3 different sampling amounts: 64, 32 and 16. The render time of a frame of the 64 sampling-amount is around the 15.5 minutes, while the 16 sampling-amount only takes 4 minutes. I expected that the resolution of the 3 frames would have a big difference, but there was no difference in the resolution at all. So my question is why do we keep this amount so high while we can keep it lower with significantly lower render times? Did I miss the difference in the resolution between the frames, should there be any? Or isn't there any?
There is no right or wrong. 

A higher number of samples will result on a cleaner picture, but takes longer to render. Clean image in cycles is usually between 200 and 500 samples, sometimes even higher numbers are needed.

A lower number will show some noise, but will render faster.

The correct number is the one that works for you: Is the level of noise tolerable? Can you live with it vs the time needed to render in higher quality?