In the case that a merchant chooses to fight a chargeback, there may be a difference between the chargeback amount and representment amounts. Neither may be equivalent to the full transaction amount. In some cases, cardholders may opt to file a partial chargeback, rather than a full chargeback. This can happen if the cardholder claims they only received a portion or part of the goods/services ordered or if they only object to/dispute a part of the goods/services purchased, or if the cardholder is claiming the merchant overcharged for the goods/services. In the last case, the cardholder may only dispute the excess amount charged by the merchant.
Similarly, representment amounts can be different from that of the original transaction. According to Visa, the representment amount must be either:
Equivalent to the amount of the original transaction
A corrected amount for the original transaction
A partial amount that is deemed enough to remedy the original chargeback (in the case of second chargebacks)*
*https://usa.visa.com/support/small-business/dispute-resolution.html