We will not be refunding the deposit due to the number of guests exceeded the property limitations of six. we have video documentation. I am seeking suggestions on verbiage to be used when we submit our claim.
I don't think much verbiage is necessary. I looked at both your 6-pax listings and the rules are pretty clear that if guests try to sneak more they will forfeit their deposit. While in my opinion I do think it's a bit draconian but I fully support ability your right to do so, especially when it's so clearly stipulated. Maybe something to the effect of "per house rules we request full forfeiture of guests security deposit due to excessive guest count. Video confirmation available upon request."
Unfortunately, there is no actual deposit. You can submit a claim for more money but if the guest refuses to pay then Airbnb will intervene. There are mixed results on whether Airbnb will issue more money or not based on extra guests. Please let us know how it works out.
@Peter1037 as Emilia already mentioned--Airbnb does not actually collect a security deposit from guests; this is just another gimmick of theirs. Have you already contacted the guest and asked for the extra guest fee? If the guest is not responding/refusing, you should contact Airbnb asap.