Discrepancy between Garmin and Xert dashboard

Why does it keep happening lately that the targets from the “magic buckets” on my Garmin 1050 don’t match the results on the Xert dashboard? Today, I filled the buckets precisely—down to the decimal point—yet the dashboard showed I had done far too much.
My Garmin was connected to Wi-Fi, my fitness signatures were up to date, and I didn’t have a breakthrough.