Confused about shade
i have a north facing garden. I have a border which is in shade and doesn’t receive direct sunlight due to a retaining wall. When the sun is behind the clouds it isn’t any darker than the rest of the garden as it’s very open to the sky and gets lots of indirect light. I’m trying to figure out appropriate plants I looked at RHS website which says Light Shade is “ A site that is open to the sky, but screened from direct sunlight by an obstacle, such as a high wall or group of trees” but also in a separate part of same article says “in practical terms if a site receives less than two hours of direct sun per day, it must be considered to be heavy shade” lol so am I dealing with light or heavy shade? Also online nurseries tend to categorise into “shade” or “part shade”. Which should I pick? Confused.