I just looked it up and it seems you are right, I am really sorry for the insult.
However, the McMichaels were still not justified to kill Arbery, even under the law of self-defence. This is because in the state of Georgia, the initial aggressor cannot claim self-defense when the person they aggressed upon retaliates: "There are three situations in which a person is not justified in using force (I will only list this one): If he initially provokes the use of force against himself with the intent to use such force as an excuse to inflict bodily harm upon the assailant".
The McMichaels attempted to arrest Arbery while openly carrying guns, and while both is legal in Georgia, Arbery is also entitled to self-defence. As he was not the aggressor in the situation - the McMichaels had their guns out when Ahmaud Arbery came jogging towards them - it is clear that they were willing to use deadly force even before Arbery had done anything that would've warranted them to do so. Citizens arrest using deadly force can only be justified if the arrester was practicing self-defence or was trying to prevent a further more serious felony from being committed, but because they had already pulled out their guns before Arbery had done either (attack them or commit a felony) it shows that they were the aggressors in this scenario, and not Arbery, which is why the case for self-defence isn't viable.