Real Time XSS versus Completed Activity XSS

I have an issue where the real time accumulated XSS on my Garmin shows much higher at the end of a ride than what is reported after I upload the activity. Often the difference is about 10%. The differences are greater for hard group rides or intervals.

Yesterday’s hard group ride was a much larger difference, 235 XSS on my Garmin versus 162 XSS. I’m guessing the uploaded version is correct. Can anybody explain the difference and how that can be corrected?

Which Connect IQ app?
Are you running latest version of the app?
Are you sure your Fitness Signature was synced prior to the ride?