Sorry dude, don't know then. I only have the Wii U version so I can't try it out for myself.

No, it was the map where you unlock Darunia's great sea outfit. 

Was it a "trigger the magic circle" map? If you trigger one then it bombs up a few strongholds and all the KOs get added to your total.

Have no pictures as it happened all of the sudden, but I was doing a get lots of kills mission on the Great Sea adventure map and suddenly went from 600(or so) to 1800 kills. 

Not sure what I did to activate it, but I switched to my second character while attacking a giant boss' weak point and the kills jumped. Wondering if anybody else has experienced this. 

Bizarre Glitch in Legends.