Thank you for your post & my apologies in the delayed response.
This normally happens when the model/dialog units are different from the default units set for each country material library. This means that if you have the USA material library installed (which is imperial) but your model/dialog units are metric then this kind of issue may appear.
Please follow the steps below as they should fix the issue.
1. Go to 'Window > Model Units' & make sure you . Note: This can also be selected when selecting a template when SketchUp is launched.
2. Go to 'Extensions > PlusSpec > Settings' & make sure you have the correct material library installed (currently there is only AUS, USA & UK so you must pick from these).
3. In the same dialog (Settings Tool), make sure the Dialog Units are set to the correct option according to whether your model units are imperial or metric (i.e. metric = AUS or UK, imperial = USA). Note: By default this will be set to use the model units which were set in Step 1.
4. Go to 'Extensions > PlusSpec > Restore Factory Default', which will return your dialog option & values to factory settings.
Would you be able to please let me know if this fixes the issue you're having?