MC Link pulls your activity data from the Health app that is pre-installed on all IPhone devices. If the data in your Health app does not match the data from the Apple Watch this is an issue you would have to address with the Apple support team as it would be an issue with how the watch is talking to the Health app.
To make sure that your Health is showing the correct data you can adjust the priority of the data sources the accepts data from. Instructions on how to do this can be found here: https://support.apple.com/en-us/HT204351
An alternative option is to turn off the Fitness Tracking feature of your IPhone itself; this prevents the Health app from counting steps from the movement of your phone effectively limiting the health app to using your Apple Watch data only. The Fitness Tracking feature is found in your IPhones settings under Privacy->Motion & Fitness