Don't know if this was introduced before but what does "+=" serve as? I can't seem to figure out its utility and why the tutorial would have it without explaining what it does. It seems to served as a shortcut for total = total + a list. It's just overly confusing and needs clarity.
They kind of skip this explanation, but it seems to just be shorthand of repeating the total in the equation.
total += prices[item]
is the same thing as saying:
total = total + prices[item]