So if understand this correctly this system enables one correction in flight as it has to eject all the bolts not to leave the projectile unstable, while the sequence of ejection determines which way  it can correct.  

Wonder by how much it can alter the trajectory and is the trajectory change possible in every stage of the flight or just certain point as it seems the system of one nudge has to pick a specific point in flight to get the desired course change. 

Yes, it seems to be a single course correction -- it just times the ejections so they push the shell in the desired direction.  The seeker needs to be able to sense the target and have a pretty good measure of what the miss distance/direction is going to be.  The less the estimated miss distance, the later the correction can be.  Seems like it's probably fairly late in any case, judging by the test video.  That means the rounds need to be at least close to on target anyway. But against small boats, turning a near miss into a direct hit is a big improvement.  

The other interesting bit is that the seeker also serves as a delay fuze. The round doesn't necessarily rely on impact or a separate proximity sensor; it activates based on estimated time-to-go from the seeker.