No definitely 390mm
The only thing I can think of is that all the others would have been on the car for 3 years or more and covered around the 30k mile mark. I changed to coilovers after owning the car around 3 or 4 months and around the 3k mile mark (it was sat at 390mm back then as we used this as a bench mark for the coilovers). I re-fitted them around 2 or 3 months ago but have only covered around 200 miles since.
There's two things that could happen here, either they sag by 15/20mm over time (quite possible as most seem to be lower at the front/heavy end) or I have random springs that shouldn't be on there?
Just to confirm, are we measuring from the centre of the Alfa badge in the wheel or the top of the badge in the wheel?