Polarity of capacitor on PCB
The polarity of electrolytic capacitors is marked on the body with an arrow with an embedded - sign pointing to the base.  The lead closest to the arrow is the negative pin for the cap.

As shown on the electrolytic cap immediately to the right of the removed part location, the thickened part of the outline is where the negative lead of the cap goes.  The + mark on the legend is indeed for the + lead of the removed capacitor.  So the decal has two markings to indicate polarity.