It is the fee charged when a piece of checked baggage weighs over 23 kg (the weight limit is 32 kg per piece).
An overweight baggage fee is charged in addition to the checked baggage fee.
Please refer to the Table of Check-in Baggage Fees (PDF) for the fees.
*Overweight baggage fees can be handled only at the airport counters.
Reference Please tell me the number, weight, and size of baggage I am allowed to check in.