Help with shipping cost

im new to vented .A buyer bundled 11 items, I didn’t think about it till after but what if all those shirts combined makes the weight go up 2 or 3 pounds. It looks like the highest they have is 4 pounds. It doesn’t let me change anything. Will I get charged the overage? I know this is free shipping promo but will I get charged ? The shipping methods are speed x and USPS