Something seems odd in the Block History for block #680 (170290), though it's probably just something I'm misunderstanding.

It says block #680 finished at 2:52:10, and corresponds to block 170290.  Block #681 finished 4 seconds later at 2:52:14, and corresponds to block 170305.  Were there really 15 blocks found on the network in that time period?  Blockchain.info shows 170305 as found by EclipseMC (as expected), but 170290 is showing as found by Bitclockers.  Any idea what's going on?