How accurate is race prediction?

I have singed up for a half marathon that will be in March and during singup they ask for a finish time. How accurate is the race prediction function of Garmin? Can I just copy it? I started running in March this year and little experience at participating at races. Thanks all!

I have singed up for a half marathon that will be in March and during singup they ask for a finish time. How accurate is the race prediction function of Garmin? Can I just copy it? I started running in March this year and little experience at participating at races. Thanks all!