This is probably one of those moments when I'm simply blind, but in the example on p. 176, it implies that having two environmental modifiers of the same level (-1 in this case), bumps the modifier to the next level (-3); that is: they aren't cumulative (-1 + -1 = -3 in Shadowrun math). Where is the rule that this example references?

Pg 173

To determine the Environmental modifier, take
only the most severe environmental condition and
use the associated modifier. If there are two or more
environmental modifiers tied for most severe, bump
the modifier up a category. Note that Range is an
environmental modifier.