It's impossible to say whether or not X points is correct for a given change. It depends on the scoring model, your credit profile and the change in your revolving utilization (not the same as DTI as all debts are not considered the same way). If your revolving utilization changes sufficiently -- and maxing a card is certainly sufficient -- then you should expect a score drop.
Keep in mind that the general advice is do not exceed 30%. Ideal is, however, much lower. Short term high utilization generally isn't an issue but prologned high utilization can lead to adverse action.
