Hi ​@Cam_Ninja,

welcome to the community hub!

First I want to say I don’t know why STRAVA shows 5 km less than GARMIN but I an idea came up:
have you tried to download the fit/gpx file(s) from your GARMIN Watch and upload it to STRAVA manually? 

Is it the first time it happened? All you preious runs showed the same data?

I would try to download the .fit or .gpx file from Garmin and upload it to Strava like ​@cy-linder mentioned.  Looking at your Strava file, the lap pace pretty well matches what your Garmin activity is showing (6:09 min/km give or take), but is only showing 10km.  Since it is showing essentially the same time in both files, it looks like the file may have been corrupted in some way in the transfer from Garmin to Strava.  You may have to delete the existing Strava file in order to manually load the .gpx or .fit file from Garmin, but you can try without doing that first just to see.  

My distances/elevation between Garmin Connect and Strava also always differ, but not just in that respect.
When I cycle long distances with our club that include a fair amount of elevation gain, our elevation gains in Strava can also vary significantly. This is despite us always riding alongside each other in a single group.
Many of us also use the same GPS, but despite this, one person might have gained 200m more elevation gain than another over a distance of less than 100km.