My anatomy scan was at 21 weeks, I had a level 2 scan the next day and the first one they told me 1 lb 2 oz (510 gms) and the next day I think they said 1 lb 4 oz (567 gms). From what I found online, this was about the 50th percentile. But, I'm sure the baby didn't grow that much in a day, so scan weights are but a rough estimate. By my scan at 25 weeks they said baby was 2 lb (907 gms).
My 25 week scan he was measuring about a week ahead and at 21 weeks was told it was a few days ahead. So, I don't think your 386 gms is big.
But...my family grows big babies, 9-10 pounds.