The four screws are holding the plastic "unit", which the sub is in. However the plastic unit is too large to pull out after removing the screws. The rear deck is overlapping the sides of the plastic unit.
I don't know how the sub is connected to this plastic unit, hopefully there is another set of screws hidden, that will be visible once the unit is removed. I'd rather not pry the adhesive off if thats what is holding the sub in; i want the removal to be reversible so if I get rid of the car one day(LONG time from now hopefully

) I can put it back in. It works, but I have a set of 10" subs in my trunk that I'd had in previous cars, I'd rather use them. The bottom of the stock sub is interfering with the top of my sub box in the trunk.
Fingers crossed for screws NOT adhesive!