FTP did not Update following race effort

My FTP is 248W. I just did a 30km (48 mins) race on Zwift and Zwiftpower had my average power at 256W but I did not get an updated FTP in Zwift.

Any ideas why not? TIA

I’m pretty sure Zwift would take 95% of the best 20-minute period of your 256W average workout, so that’s not guaranteed to be better than your current FTP of 248W.

According to Riegel your FTP would be 252 watt.

thank you Steven! I’m a bit of a newbie to cycling yet so I appreciate the response.

Thanks Alexander! I’m just figuring out this cycling thing, appreciate the response.