The problem is, you can't enter the cycled distance in Forerunner 45 before it sends the activity to Strava.I think that is only possible in garmin connect on pc.
The only way I am aware of, is disconnecting Strava before you save the Activity, and then reconnecting Strava again, afterwards. You would then need to import the activity manually to Strava. Frankly told, it may be simpler, deleting the activity from Strava, and importing it again manually.
However, I believe Strava will still report the original distance, and not the edited one. You would have to export the activity in the TCX file format, and edit the distance in it manually to get the desired value into it.
