Why does Garmin the personal records for running not split in outsider running and running in the gym? That are two complete different things.
Personally I dismiss all records from a treadmill, since they do not interest me, and keep only outdoor records. You can do so too. You can also delete such records, if you already accepted them by mistake.
Hi Trux, how do I dismiss a record?
You can do on the watch (but perhaps not on all models), with the phone app, or on Garmin Connect Web. Personally I prefer Garmin Connect Web:
https://connect.garmin.com/modern/personal-records