14/40 simply means swapping your front sprocket (std 13t) to a 14t, keeping your stock rear 40t in tact. This will increase your mid range and top end pull, slightly, giving you a wider more taller powerband and overall better taller gears which results in a nice strong feel over the stock short stroked blasty personality.
Go for it, cheap easy, very nice upgrade that is loved by many blaster riders...
Do keep in mind though that sometimes, in some cases, your stock length chain might give ya a bit of trouble getting back on, might have to adjust your tighteners to move the axle forward a bit to get re-adjusted.