If they can get it into a small package, ten seconds would be plenty for an air-launched anti-ship missile. Less fuel weight equals more warhead size for the same total weight
If we and you are only really concerned with ten seconds or so why use a scram jet to begin with as such a propulsion system relies on a rocket to bring the craft up to speed to allow operation of the scramjet? Rockets work fine for short distances where velocity is crucial such as shooting down an aircraft or bringing down a missile but for larger, slower targets in the atmosphere, there is the cruise missile. Air breathing, hypervelocity aircraft are still a research program and will be for some time to come.