With the Shippo module you get a Shippo settings card: Weight per Meal (lb), Weight per Box (lb), Max Meals per Box, Box Length/Width/Height (in), Dry Ice Weight (lb), Insured Value Default ($) and an Enable Dry Ice switch.

In the current version, only some of these actually affect the Shippo rate request: the weight sent is meals × Weight per Meal (falling back to the integration's default per-item weight if this is blank), plus the Dry Ice Weight when Enable Dry Ice is on; the insured value is capped at $100 and passed to the carrier. Weight per Box, Max Meals per Box and the Box Length/Width/Height fields are saved but are not read anywhere in the rate or label calculation – the parcel size Shippo actually quotes and ships with comes from the Parcel Template chosen in the Shippo integration settings.