Pretty sure OS X and macOS should be combined, not doing that feels like amateur hour, very puzzling. But even with that in mind, you see wild ups and downs as large as 3.5% a month from 10/24 to 11/24 to 12/24 to 01/25 and there’s no way in hell actual deployments are fluctuating like that. Error bars like that make a number of 5% pretty meaningless, however feel-good it is.

Also, for people unfamiliar with the Apple ecosystem: the OS X => macOS rebranding happened back in 2016, IIRC the Safari user agent never ever included macOS (Safari on M4 Macs running latest macOS 15.5 reports itself as “Intel Mac OS X 10_15_7” in its UA), so absolutely no idea where they’re getting this new “macOS” category. Maybe they publish technical details of their methodology somewhere? I can’t bother to check.

Don't confuse percentage points with percents.

25%+-3.5% means it's 5%+-0.7% for proportional error bars. They don't have to be linear, true, but they are certainly not 5% +- 3.5% either.