A more thorough explanation:

An amendment after payment of issue fee refers to a modification made to a patent application after it has been allowed and the issue fee has been paid. This amendment is not a matter of right and must be accompanied by a petition to the Commissioner showing good and sufficient reasons why the amendment was not presented earlier.

For example, an applicant may want to narrow or eliminate some claims in response to an examiner's rejection. In this case, the applicant can submit an amendment after payment of issue fee to address the examiner's concerns and improve the chances of getting the patent approved.

Another example is when an applicant wants to make changes to the specification or claims, change the drawings or the list of inventors, or submit prior art after the notice of allowance has been mailed. In this case, the applicant can submit an amendment after payment of issue fee to address these matters.

Overall, an amendment after payment of issue fee is a way for applicants to improve their patent application after it has been allowed and the issue fee has been paid. However, it is not a guaranteed right and must be accompanied by a petition showing good and sufficient reasons for the amendment.