16 vs 18 Gauge!

Hi all!

I got 2 cartilage piercings (helix and tragus, if that matters) on my ear a week ago, the piercer that did it told me he pierced it at an 18 but that when I change the jewelry I could use 16 or 18 gauge jewelry. How is that possible when 16 is obviously a little bigger then what I have in now? Wouldn’t it be painful?