Not a Silly Question at all!
I have actually been thinking of attempting to sort it out, beening we are getting in to summer, being able to open the sunroof would be tops!
But from the look of it, they have opened the sunroof and put a small bead of silicon around the opening and then shut the sunroof, and smoothed out the silicon that has escaped, top and bottem.
I reckon they have done this cause the weather seal on the outside has worn though and must have been leaking, and as im finding out, sourcing a New OEM sunroof seal, is a challenge, from my findings nissan only sell the seal with the whole sunroof.