Tecnica Boot Shell Size

I have 2 pairs of Tecnica Icon Alum Comp boots. On the bottom of one pair of boots is a 9 1/2. The other pair is 10 1/2. I assume they correspond to shell sizes, but I am curious what these numbers mean in the world of numbers and sizes? Are they like a UK shoe size?

It means you have mis-matched feet.

They are indeed UK sizes.

The Icon was the last Tecnica model to use this sizing. The Diablo is a true mondo-point size scale.