I would advise simply not worrying about it. When you are off the pedals however you will have the pedals for reference so when you want to do a FTP type ride outside it is your pedals that you will be listening to so remembering that number will be more important than remembering the numbers from a smart trainer . It would be interesting to note power ratings when riding with somebody that is the same weight as you. If they read the same power as you do with your Garman power meters then you would know that they were reasonably accurate . That assumes that you were on at least similar bikes .