We're all beginners at something, so don't worry about being new. I still learn everyday around here- that's why I stick around.
I'd have to guess at the reasons it's darker than you'd expect, but I'm guessing it's simply because extract tends to darken. Even the lightest extract is a bit darker than an AG mash. There are some things you can do to minimize the darkening. One is to add the majority of the extract at flame out. It'll still dissolve, and sanitize, but it'll keep it from darkening too much. Also, use the lightest and freshest extract you can find. I would say that it would be very difficult to make a beer with an SRM of 5 with extract, even adding the extract late.
The beer WILL look darker in the carboy than in the glass, though. When you take a hydrometer reading, hold the test jar up and you'll see it's much lighter than in the carboy. It's probably no where near a 20 SRM, if you meant for it to be a 5 or 6.
The calculators don't seem to be very accurate in judging color, even for my AG batches. Sure, they take the "20L" and "80L" in ingredients and calculate the color, but it seems like it's only close at best.