Providing the label supplied is the Recommended size/weight, ie you didn't over-rule it when you did the listing, it doesn't matter. I've sent several things that have been over-weight/size with no problems to either me or the Buyer. The only catch is that if it's going Royal Mail it's got to be less than 20kg and less than 62cm (two feet) long. For Evri it's 15kg and 120cm.
Cacas vendit.