Third Party Website-Sports Activity Data Handling
Some take the data as is while others reprocess it and apply their own calculations and smoothing algorithms to it. This second instance will result in discrepancies between the watch and the site, causing issues like you are seeing. If you are sure the watch is correct then it is better to ask them as they have a better idea of what they do with the data after they import it.
Many programs recalculate the data instead of using the raw numbers which will lead to inconsistencies.