I'm fairly new to Garmin and not too long ago got a Forerunner 265, which i'll be using primarily for running.
I'm still exploring the features, and today I decided to try out the PacePro feature. I wanted to try to beat my PB on a current 3K route, so decided to set my target time of 12:30, hoping to shave a few seconds off my current PB for that particular route, which is 12:39. For some reason, the pace that Garmin gives me means is not achievable for me at the moment (4:02), and would potentially result in me shaving off nearly 30 seconds. Why does it do this? I set my target time to 12:30 so 4:02 is a big overshoot.
I decided to take a different approach and set a target pace of 4:10, however when I ran with this it set me difference paces for each kilometre.
I appreciate i'm never going to run the exact pace, but if i'm aiming to use it to beat my time them it seems no good Garmin setting me a pace that's unachievable for me.
I welcome any advice.
Thanks 
Warm regards,
Luke