I need some help wiring a combination switch/GFCI outlet in the following situation. The second diagram is from the instructions and seems to match my situation, however they have an outlet downstream rather than a lightswitch (is this irrelevant?) and there are 2 black cables coming from downstream which seems to be a mistake that I need clarified.
The existing wiring is a big mess:
Looking into the back of the box:
An illustration of the current wiring: