Can you spot the difference, apart from the colours? Well, I downloaded the package and used the settings suggested to print the first ball. Then I made some slight changes and printed the second one. They were both printed using Creality Hyper PLA (Rainbow). The one on the left was printed first, then the one on the right. The two photographs showing a single ball give a big clue. I've uploaded the printer settings for the one on the right, which came straight off the bed in perfect working condition. It only took 1h 35m to print, so it's quick and easy to try it yourself. The answer to my original question is 0.4mm. The reason being that I lowered the model 0.4mm, so the attached brim was no longer visible, and told the slicer I didn't want a brim. If you get good adhesion to your print bed, you shouldn't need a brim, and the resulting print is much cleaner on the bottom, with no brim to remove. Perhaps the original author would like to add a version of the ball without the brim for those of us who would rather not have it, so that we're not 0.4mm short?