Battery Cycle count 253 with 46% capacity only??

My 13" MBA (mid 2012, purchase July 2012) is showing 253 charge cycles now, and it lasts only about 2hrs on battery. When it was new it use dto last >4hrs, probably 5hrs.

CoconutBattery says its 56% capacity.

Genius bar diagnostics says it's 46% capacity; I intened to replace the battery.

But it seems to me that the deterioration rate is too fast? Is it possible that I actually had got a 'bad' battery to start off?