That looks good,you might want to bump your temp up a bit,mine form a complete scoby cap in 6 days. When you walk past it and smell something like vinegar you can start tasting(that is why a tap on the bottom of your vessel is important). At first you will let it go until perfectly tart for your liking and then bottle. Once you have that time frame down you can start to bottle earlier and get the tartness and carbonation you want. I bottle 3 days before it's tart enough and add a small amount of sugar and get perfect carbonation,if I wait until it's perfectly tart in the fermentor, then the carbonation is lack luster.