Yea that little girl is nowhere near 4 oz, id say you may get a 1/2 oz if you train her properly. Why dont you go buy a 5 gallon pot, transplant her, let her veg prefrebly under some T5's for a month or two, then when you flower her under that 400 watter if you scrog and train her right, she will most likely hit 4 zips if not more.
Honestly you say your a new grower, stop worrying about weight and yield. You will most likely still be buying cannabis until your growing skills have gotten better, everytime i see people trying to cut corners to get big yields stop growing after a few runs. Most likely becasue they set expectations like achieving a 1/4 pound of there first ever plant. Its unrealistic and will only dissapoint you. Just grow and germinate as many seeds as you can fit, kill some plants, get your hands dirty, and dont be pissed when your little terra cotta potted plant only throws a 1/4 ounce, the big yields and skills will come with time and experience. Dont give up and dont take all advice 100 percent, the internets filled with techniques and teachings but seriously dosent mean shit unless youve done it yourself.
Dont be discouraged from some of the posts, my best advice is to just lurk lurk and more lurking on as much information as you can take in. Start up some PM with people who are growing how you would like to grow, and ask for some advice. But be careful with asking before doing resaerch, people will flame you for not doing your homework, and give up on trying to help you out if you always have questions that are easily awnsered.
PS your light years from a CO2 system, thinking about a sealed room with CO2 and pulling max yields are gonna cause you to flounder. This plant wants to grow, and you can make your grow as simple or as complicated as possible, but that will all come with time if you stick with it. For now just remember to water them, and give em some food, and enjoy growing the most unique, beneficial substance ever created by our goood lord(Thank you Baby Jesus!! hah jk) but sort of serious.