I don’t know rocket man ...The Salomon SX sizes are their own circumference-based scheme.
My size 345 boots have a 321 mm BSL.
They are equivalent a 27 or 28 traditional boot which would typically have BSL in that same neighborhood.
From my Lange memories
26.5 = 306
27.5 = 316
28.5 = 326
That makes it a 28
Whatever that really is