Hi Wing,

Just to confirm you were still using a mining pool at this stage? I am looking at my own personal wallet, it also comes up with the mined type when I was using the p2pool pool early stages
and using the normal pools before I did a wallet update. Now I get Received with as Type when mining.

In terms of the times coming all in at the same time, this happens when you start your wallet up, it uses the time of when the block sync takes place.

IE. if you haven't opened your wallet for 1000 blocks and anything you've earned during that sync will show up with that time.

Let me know if that clears up things for you?