Seeing as it's your first grow, with a total of 180w of cfls, which is nowhere near enough light for sufficient flowering of a plant of that vegetative size (wait till you flip and the plant doubles in size - the cfls will lack quite a bit of light penetration), I would estimate around 1/2 oz to a full oz if you're lucky. 3-4 oz is a gross overestimate unless you plan on using way more lights for flowering.