When using the Pack IQ plugin, it is important to consider the dimensions and weight units of the boxes. The units are independent of the WooCommerce store units. To change the units go to WooCommerce -> Settings -> Pack IQ -> Settings.
You can change the weight unit to g (grams), kg (kilograms), lbs (pounds) or oz (ounce). On the other hand, the dimensions unit can be changed to mm (millimetre), cm (centimetre), m (meter), in (inch), or yd (yard).
Please note that once you change a unit, this will affect all the already saved boxes, so make sure to adjust the boxes to the new unit.