Sounds to me like you may have received an installed spare

There shouldn't be more then 2 water level adjustments on the sump. Let me peak in my box and see if either of mine are pre-installed.
Ok so looking at mine, #8 and #9 are pre-installed. My #10 is not pre-installed. I have a black piece as well as a blue piece the looks exactly like yours. I noticed on my #8 and #9 they attach with 2 piece on each side of the opening. I'm assuming for #10 the install should be the same, the black piece plus the blue piece with the sump divider itself in the middle of those two.