How would I take a gui position and add a variable's value to a specific part of it?

On for example YouTube theres a bar showing how far into a video you are. Well thats what I've tried here.

local e = script.Parent.Parent.Time
while true do
	if e.Value > 0 then
		wait(1)
		local b = script.Parent.Parent.Far
		b.Value = 393 / b.Value
		e.Value = e.Value - 1
		script.Parent.Position = UDim2.new{0, b.Value, 0.5, -25}
	else
		wait(1)
	end
end

Notice though on line 8 where it says 'b' i want it where the guis normal position is which is {0, 0, 0.5, -25} but + the value of b if that makes sense. but i dont know how to do that, I've dont usually work with guis that much.