TL:DR: they don‘t accept offsetting carbon emissions. By that logic, one watch has emitted between 7 and 12kg of CO2.

Note from my side: driving a combustion engine car emits between 100-200g per CO2 per km. So driving 70km in your car, will equal one Apple Watch.

So it is still quite impressive how low the value for the Apple Watch is, but it is not neutral.