It's called bedding in, you can see in the first image that the spades haven't dug in yet.
So do you think this was a real fire mission or just a drill to make the spades dig in and test the crew? Don't really know much about artillery procedures.
I do have to say though I'm surprised to read that the M777 is a recent development. I was under the impression that modern artillery had shifted almost completely to self propelled guns to escape counter-battery fire?